Season 1 of 9-1-1 (2018) introduces the high-stakes world of Los Angeles first responders, following a team of firefighters, police officers, and dispatchers. Unlike later seasons which often open with massive multi-episode disasters (like tsunamis or earthquakes), Season 1 focuses on character introductions and the "emergencies of the week."

Season 2 of 9-1-1 is widely considered the season where the show truly found its footing, doubling down on the "found family" theme and introducing massive, cinematic disasters. It also marked a significant cast change with the arrival of Jennifer Love Hewitt and Ryan Guzman.

Season 3 of 9-1-1 is widely considered the show's peak for high-stakes drama and production value, defined by one of the most ambitious disaster sequences in television history and significant personal growth for the 118 team.

Season 4 of 9-1-1 (2021) is set against the backdrop of the COVID-19 pandemic, though the show incorporates it as a "new normal" (masks, social distancing, and vaccines) rather than making it the sole focus. This season is known for its high emotional stakes and the long-awaited payoff of several character arcs.

Season 5 of 9-1-1 focuses on the theme of "starting over." While it features the usual high-octane emergencies, it is heavily defined by the temporary absence of several main characters and a major shift in the 118 team’s roster.

Season 6 of 9-1-1 focuses on themes of leadership, recovery, and the long-awaited evolution of the main characters' personal lives. While it lacks a single, city-destroying disaster like previous years, it features several "mini-arcs" and intense emotional payoffs.

Season 7 of 9-1-1 marked a major transition for the series, moving from its original home on Fox to ABC. To celebrate the move, the season opened with a massive, cinematic three-episode event and leaned heavily into long-awaited character developments.

Season 8 of 9-1-1 is an emotional rollercoaster that completely shifts the foundation of the series, marked by the departure of a major lead and a "passing of the torch" for the 118.

Season 9 of 9-1-1 (2025–2026) is the first full season set in a world without Bobby Nash. The season centers on the theme of "moving forward while looking back," as the characters navigate their grief and the massive changes at the 118.