Though firmly religious, Ned can be quite timid and something of a pushover. He is also often insecure. He is obsessed with following the Bible as literally as possible (even "the stuff that contradicts the other stuff") and is easily shocked when challenged on any point of dogma. This has led to his frequent calls to Reverend Lovejoy ("I... I think I'm coveting my own wife!") who has become increasingly frustrated with Flanders ("Ned...have you thought about one of the other major religions? They're all pretty much the same.") Lovejoy has been driven into severe depression by Ned's constant badgering and he now encourages his Olde English Sheepdog to defecate on Ned's lawn in order to passive-aggressively avenge himself.
Ned's sons have been raised in an unbelieveably strict climate of Christian morality, to which they seem to conform almost instinctively. In one episode, it is revealed that they "don't believe in flu shots", much as their father considers insurance to be a "form of gambling" and dice games to be "wicked" (apparently, games for Nintendo systems like Super Noah's Ark and Bible Blaster do not share in this evil; but the episode Lisa's First Word seems to contradict this as when Bart goes to the Flanders' he sees Rodd and Todd as playing with this). Rod and Todd go to bed several hours before sunset. They are not allowed to consume sugar (aside from one memorable incident involving pixie-sticks); rather, they delight in nachos "Flanders-style" ("That's cucumbers and cottage cheese!") and wintergreen "ice milk".
Most of the entertainment enjoyed by the family involves religion in some way. For instance, the family uses at least five different versions of the Bible to play "Bombardment...of Bible Questions!" ("The bridal feast of Beth Chadruharazzeb!?"), and are part of a competitive bowling team called the Holy Rollers (their uniform consisting of a Franciscan Friar's robes). Ned seems to sense that he cannot completely shield his family from the vagaries of popular culture, but does his best to mitigate the effects; one of his children's stories concludes: "...and Harry Potter and all his wizard friends went straight to Hell, for practicing witchcraft." Also, though they have satellite TV, nearly all of the 230 channels are blocked out — likely for the best, as one episode of Itchy & Scratchy was enough to more or less permanently scar Rod and Todd. (Maude once crusaded against 'violent cartoons', as well, so blocking out the channels may have been her idea.) Todd used to watch Davey and Goliath, but, finding the idea of talking dogs to be blasphemous, he has since stopped. Ned and Maude did have a subscription to Newsweek magazine, however, which may have been the means by which they followed outside goings-on.
Ned can sometimes fight for what he believes in, especially when faced with an equally zealous or entirely apathetic opponent. For example, when Homer and Bart became Roman Catholic, after having shaken a Catholic priest's hand, Ned reminded himself to get his hand "re-blessed". In the same episode, when Bart told him he wanted to convert to Judaism, Ned took out a bottle of chloroform in order to dissuade him. Likewise, when Lisa converted to Buddhism, he ordered Rod and Todd into the bomb shelter, telling them that they might never return to the surface. He once attempted to forcibly baptize the Simpson children, using his portable baptizin' kit, after finding out that they had never undergone the ritual — and after fainting several times.
His antipathy toward Judaism and Hinduism has been lightly portrayed — he once compared worshipping Shiva to asking for help from Hawkman, and he fears that his children will grow up to become Jewish Hollywood producers.
In the episode in which Homer has a crayon removed from his brain and thereby becomes super-intelligent, Homer states "Hey, Flanders, I was working on a flat tax proposal and I accidentally proved there's no God". He hands Ned a piece of paper with the proof. Skeptical, Ned says "We'll just see about that." Ned reads the paper, his face falling. "Nope, it's airtight. Can't let this little doozy get out." Ned then uses a lighter to burn the proof, while, in the background, Homer puts more copies of his formula on the windshields of nearby cars. (However, God has made several appearances on the show — in dream sequences, particularly.)
Despite his intolerance towards other religions and beliefs, he is still honest and sincere in carrying out the Christian doctrines of charity, kindness and compassion. He spends every Wednesday working at the Springfield homeless shelter and soup kitchen — the Helter Shelter — and reads to sick children at the hospital, where he had unknowingly seen a softer side of Moe: "If this gets out, the next words you say will be muffled by your own butt." He is rigorously honest and upright, even going so far as to spend an entire day tracking down a Leftorium customer in order to give him the extra change that he had previously failed to hand over. In a similar vein, after winning football tickets by answering a radio trivia question, he immediately asked for the cash value so he could report this on his income taxes. He also means to be a good neighbor to the Simpsons, regularly asking about their lives and offering his assistance — and then suffering the consequences often paid to those with good intentions.
Ned is very selfless and often brave — though angry apes can faze him. He once risked his own life to save Homer from a house-fire, and has promised to donate one of his kidneys and lungs to whoever needs them first.
When a comet threatened to destroy the city, he attempted to save every single Springfieldian, and even decided to leave his own bomb shelter — Homer having told him he would be useless after the apocalypse — instead of allowing someone else to die in his place. It is interesting that the rest survived only because they decided to follow Ned's brave example, or felt guilty about letting him sacrifice himself: if they had stayed inside, the shelter would have collapsed upon them.
Ned has fed, bathed and clothed at least one indigent man — Homer's half-brother Herb, before he created his second world-class business. It is a telling fact that both Rod and Todd wanted to anoint the sores on Herb's feet.
Ned Flanders is a basically good-natured and kind-hearted man who tries to follow the teachings of Jesus; that this often makes him the target of those less scrupulous than he seems merely to be a badge of honour for him.
His dogged friendship can inspire the loyalty of others; when his Leftorium seemed sure to go bankrupt shortly after it opened, Homer came to find that many people in Springfield love Ned: "Ned Flanders is in trouble?!" shouted a man, learning of the predicament and leaping off the couch. Homer was thus able to set the stage for a Frank Capra-esque George Bailey-bailout.
Flanders' religious denomination, along with that of Reverend Lovejoy and most other Springfieldians, has long been a matter of much speculation among fans. In The Father, The Son, and The Holy Guest Star, this is briefly mentioned by Reverend Lovejoy when stating that they will bring Bart and Homer back to the "one true faith": The Western Branch of American Reformed Presbylutheranism.
He has compared flood to the tale Noah's Ark at least twice; when Homer flooded Springfield in "Mom and Pop Art", he believed that "The Lord [had] drowned the wicked and spared the righteous". In "Pray Anything", he built an ark himself, made entirely up of same-sex pairs (to prevent sexual intercourse). However, many people believe that this was Noah's intention; to put male-female animals on the ark as they were responsible for reproduction of the species.
His religious fervour has been mocked most openly in the many Halloween episodes, outside of regular continuity. He has: become "the unquestioned Lord and Master of the world", instituting Orwellian "Re-Neducation" facilities for those who have impure thoughts, complete with frontal lobotomies for hardcases; proclaimed his preference for "wanton carnality" as an early Pilgrim immigrant to the New World, only to be vetoed by Maude; been transformed into a werewolf; been murdered by both Homer Simpson (who used the rise of a zombie horde as an excuse for killing him — Homer didn't care if Ned was actually zombie or not) and an evil bus-gremlin which he attempted to adopt. He has also been seen participating in the "Walk for the Cure to Homosexuality".
Ned has represented both the Devil and God — in a Halloween episode and in a regular episode, respectively. In the Treehouse of Horror IV special, Ned played the Prince of Darkness in the opening segment "The Devil & Homer Simpson", explaining that "it's always the person you least expect". The Ned-Satan offered Homer a donut in return for his eternal soul, but was thwarted in a court of law when it was revealed that Homer had previously granted his soul to Marge when they got married. Later in the series, when Marge fantasized about being Eve opposite Homer as Adam, Marge/Eve imagined Ned as representing God, who was never clearly seen — but His voice was certainly that of Ned, and God's arm was clothed in Ned's classic green sweater.
Ned has also represented Priam, King of Troy.
Ned is left-handed, and runs a successful (after a rocky start, anyhow) specialty store for other left-handed people: The Leftorium.