The team finished 12–4, won the NFC Central Division, and appeared in the playoffs for the first time since 1983. It stands as the team's best season since the NFL-AFL merger in 1970.  The Lions finished the season undefeated in the Pontiac Silverdome, including playoffs, and the team did not lose a game at an indoor facility the entire season, having made trips to Indianapolis and Minnesota during the year.
Statistics site Football Outsiders summed up Detroit's season thus: "The Lions were one of the most inconsistent teams of the year, which is what happens when you win 12 games but lose 45–0 (to Washington) and 35–3 (to San Francisco). Otherwise, it's a little hard to tell why they ended up only 17th in [efficiency]. The Lions didn't have too many super-close victories, but did go 4–0 in games decided by a touchdown or less. They didn't particularly take advantage of long plays ... with only four gains of 50 yards or more. They did benefit a little extra from fumbles on defense, recovering 15 of 23. They also benefitted from poor opponent special teams...."
Detroit, according to Football Outsiders, had "a bit of an odd schedule; on the surface, it doesn't look like Detroit's schedule of opposing run defenses was that easy. The Lions missed the [league-leading] Eagles, but they did have to play six games against the teams ranked sixth through ninth in run defense [efficiency]: San Francisco, Chicago, Washington, and Green Bay. Except running back Barry Sanders didn't play against Washington in Week 1, and he had only seven carries against San Francisco in Week 8. His two highest-carry games came against the two worst run defenses in the league, Miami and Indianapolis."
The Lions were plagued by injuries most of the season. Wide receiver Aubrey Matthews was lost for the season to a knee injury on a meaningless final play during a 45-0 loss to the Washington Redskins during Week 1. Starting quarterback Rodney Peete was lost for the season in the 9th game of the year, a 34–10 victory over the Dallas Cowboys. Second string quarterback Erik Kramer, who had won the backup quarterback job from Andre Ware (the team's #1 draft pick from the season before) during training camp, guided the team the rest of the way. Although Peete's injury was serious, perhaps the most devastating injury was the career-ending injury that befell guard Mike Utley in a Week 12 game against the Los Angeles Rams. Utley suffered a severe injury to two of his cervical vertebrae, rendering him paralyzed from the chest down and ending his career. Unaware of this, Utley gave a thumbs-up gesture to the crowd as he was being wheeled from the field. For the rest of the season Lions players wore a decal with Utley's number 60 on their helmets to honor their fallen teammate.
Utley's injury gave inspiration to a team that at that point in the season was struggling, and the team won its last six games to steal the division title away from the Chicago Bears, whose Week 17 loss to the San Francisco 49ers left them a game behind the Lions who did not lose a game the rest of the season following Utley's injury. By winning the division and having one of the two best records in the conference, the Lions earned a bye into the divisional round. There they faced Dallas, who had beaten the Bears the week before to get their first playoff win since 1982. Although the Cowboys held Lions' star running back Barry Sanders in check for most of the game, Kramer threw for 341 yards and three touchdowns and Sanders closed the scoring with a 47-yard touchdown run for a 38–6 drubbing of Dallas. It is the Lions' only postseason victory since they won their last league championship in 1957.
The win earned the Lions a return trip to Washington for the NFC Championship Game and a chance to avenge the 45–0 defeat in the season opener. The Redskins jumped to an early 10–0 lead when Kramer was sacked and fumbled on the Lions' first possession, then was intercepted on the second. The Lions fought back with a touchdown pass to receiver Willie Green and a field goal by kicker Eddie Murray in the second quarter to stay within one score at the half. The Lions trailed 17–10 at the break, but failed to score again as Washington scored 24 points in the second half to put the game away. Ware replaced Kramer as quarterback in the fourth quarter. He promptly threw an interception which was returned by Darrell Green for the game's final touchdown. The 1991 Lions' season thus ended the way it started, with a loss to the Redskins at RFK Stadium; the final in this game was 41–10 in favor of the eventual Super Bowl champions.
The Lions finished the season with a 9–0 record at home, counting their playoff win. The team did not play particularly well on the road: outside of their wins at Indianapolis and Minnesota, their only other outdoor wins came against the Green Bay Packers in Week 16, and the eventual AFC Champion Buffalo Bills in Week 17; the margin of victory in those games were four and three points respectively and the Lions gave up 30 or more points in three of their four road losses, two of which came to teams that failed to qualify for the playoffs (San Francisco 49ers, Tampa Bay Buccaneers).
Quarterback Erik Kramer led the Lions to their only postseason victory since 1957 by completing 29 out of 38 passes for 341 yards and 3 touchdowns. As of 2016, this is the Lions' only playoff win in 59 years.
The Redskins crushed the Lions, 41–10, as quarterback Mark Rypien completed 12 out of 17 passes for 228 yards and 2 touchdowns. Detroit quarterback Erik Kramer was sacked 5 times, three of them by Washington linebacker Wilber Marshall. Lions running back Barry Sanders, who rushed for 1,548 yards during the season, was held to just 44 yards on 11 carries.