Kevin (Probably) Saves the World follows Kevin Finn, a cluelessly self-serving person who is on a dangerous path to despair. In a downward spiral, Kevin returns home to stay with his widowed twin sister and niece. On his first night there, an unlikely celestial being named Yvette appears to him and presents him with a mission – to save the world.
Kevin, who is on a dangerous path of despair, returns to his childhood home in Texas to crash with his widowed twin sister, Amy, and teenaged niece, Reese. It is a strained homecoming - he and his family have grown apart over the years - and Kevin has no real hope that anything will get better. But a series of fantastic events, including a meteorite landing near the house, lead Kevin to meet an unlikely celestial guide, Yvette. Yvette delivers incredible news to Kevin: in every generation there are 36 righteous souls on Earth whose mere existence protects the world. Kevin, she tells him, is the last of the 36 righteous. Humanity has been thrown into crisis. Without the 36, the world will begin to lose the one thing that allows us to persevere through the ups and downs of life: hope.
Yvette attempts to guide Kevin in his mission to help others, but when he tries to "help" a local brewer, Kevin's good intentions go horribly awry. Amy struggles to understand Kevin's strange behavior while still mourning the loss of her husband. Meanwhile, Kevin rekindles an old flame with unexpected consequences.
On his quest to become a better person, Kevin helps a young couple plan their wedding. In doing so, however, he sees the consequences of lies - both his own and the couple's. Meanwhile, Yvette attempts to organize the other celestial beings, and Reese witnesses her uncle's strange new talents first-hand.
When the universe leads Kevin to help Lucille - a mean-spirited diner owner - with some family drama, he quickly finds himself stuck in the middle of a tricky situation with her equally difficult sister. Meanwhile, Reese entertains the thought of Kevin having special powers, and Yvette begins to struggle with the side effects of being on Earth.
After draining his bank account in service of others, Kevin looks for a different way to help a single mom who's drowning in her son's medical bills. Meanwhile, Reese uses a school project to learn more about her uncle, and Yvette struggles with the full range of human emotions.
Despite being on the outs with his sister, Kevin tries to help a desperate man find work in order to support his family. Meanwhile, Amy deals with the ramifications of invading Reese's privacy – an act that forces everyone to rethink their priorities and what it means to be a family.
Yvette has her reservations when Dave, another celestial being, pops up looking to join her and Kevin on their latest mission: Reconciling Kristin and her mother under the most challenging of circumstances. Elsewhere, Nate tries to work up the nerve to ask Amy out, completely unaware of her budding chemistry with a potential beau.
Kevin is forced to choose between completing his mission – which involves helping a talented artist find the courage to believe in himself – and attending the opening night of Reese's play. Meanwhile, Yvette makes a startling discovery about Dave, and Amy prepares to go out on the first date since her husband died.
Convinced that the universe is leading the way, a very confident Kevin heads to Laos with Tyler in search of the first righteous soul. Meanwhile, Yvette has her doubts about their mission and has a chance encounter with Tyler that changes both of their outlooks. Back in Texas, Amy goes all out decorating for Christmas and decides whether or not she's truly ready to date again.
Reveling in his success after finding the first righteous soul, Kevin attempts to help a man start dating again after a bad break-up. Meanwhile, inspired by Kevin's good deeds, Reese befriends the new girl at school. Yvette becomes concerned by Tyler's desperate search to reconnect with the mysterious lady he met in Laos, and Amy finally finds the courage to ask Nate out on a date.
As the newest substitute teacher at La Salle High School, Kevin tries to help an introverted student named Adam become more self-assured and popular. However, to do so, he must first pull off the second greatest freshman prank in the school's history. Meanwhile, Yvette contemplates life after the mission, and Amy and Nate struggle to plan the perfect first date.
When Kevin encounters a mysterious do-gooder and attempts to help her raise money for a dog sanctuary, his plan backfires bringing her secret past to light. Meanwhile, Tyler believes he has finally made contact with Yvette, the mysterious lady from Laos. Nate invites Amy to a friend's wedding only to discover his ex-wife will also be attending.
Looking to put an end to the "Lady of Laos" fiasco once and for all, Kevin travels to Canada in search of Tyler. However, his priorities quickly shift when Kevin realizes that deceiving Tyler actually means finding the next righteous soul. Meanwhile, Amy and Nate draw closer, and Yvette learns that she isn't the only celestial being susceptible to injury.
Desperate to repair his friendship with Tyler, Kevin enlists the help of Kristin to pull off a grand gesture to win him back. While working to do so, his relationship with Kristin deepens, and they meet a mysterious, strange duo who are hiding out in the middle of nowhere. At the same time, Kevin tries to help Marc, a young man who has left home in search of adventure; and Yvette and Dave continue to struggle with human tendencies.
Feeling guilty about the role he played in getting the former high school security guard fired, Kevin looks to help Becky follow her true passion: inventing. With Amy and Tyler's assistance, they enter Becky's newest invention into a local Entrepreneur Expo with hilarious results. Meanwhile, Yvette is forced to come to terms with Dave's disappearance.
Kevin struggles with the idea that his relationship with Kristin might be in jeopardy while helping a stranger honor his deceased uncle's burial wishes. Yvette makes a drastic decision regarding her future with Kevin by involving a celestial colleague named Cindy ("Saturday Night Live"'s Leslie Jones guest stars); and Amy receives an unexpected visit that changes everything.