| Career - Worst ERA | |||
| Rk | Player Name | Totals | |
| 1 | Robert Person | 5.48 | |
| 2 | Hideo Nomo | 5.01 | |
| 3 | Carlos Villanueva | 4.92 | |
| 4 | Cal Eldred | 4.89 | |
| 5 | Chuck Finley | 4.77 | |
| 6 | Erik Hanson | 4.55 | |
| 7 | Ismael Valdes | 4.51 | |
| 8 | Tim Wakefield | 4.51 | |
| 9 | Andy Ashby | 4.50 | |
| 10 | Jon Lester | 4.44 | |
| 11 | Darryl Kile | 4.20 | |
| 12 | Eric King | 4.19 | |
| 13 | Gil Meche | 4.11 | |
| 14 | Bobby Witt | 4.09 | |
| 15 | Dallas Keuchel | 3.99 | |
| 16 | Ervin Santana | 3.98 | |
| 17 | Kyle Freeland | 3.97 | |
| 18 | Shane Reynolds | 3.80 | |
| 19 | Tom Gordon | 3.78 | |
| 20 | Scott Sullivan | 3.69 | |
| 21 | Terry Mulholland | 3.54 | |
| 22 | Brandon Woodruff | 3.51 | |
| 23 | Chase Anderson | 3.35 | |
| 24 | SID FERNANDEZ | 3.28 | |
| Single Season - Worst ERA | |||||
| Rk | Player Name | Totals | Year | ||
| 1 | Cal Eldred | 7.54 | 1994 | ||
| 2 | Ismael Valdes | 5.99 | 1999 | ||
| 3 | Cal Eldred | 5.73 | 1998 | ||
| 4 | Robert Person | 5.58 | 2002 | ||
| 5 | Ismael Valdes | 5.56 | 2000 | ||
| 6 | Wally Whitehurst | 5.56 | 1994 | ||
| 7 | Erik Hanson | 5.53 | 1994 | ||
| 8 | Hideo Nomo | 5.52 | 2000 | ||
| 9 | Dane Dunning | 5.51 | 2024 | ||
| 10 | Woody Williams | 5.50 | 2005 | ||
| 11 | Tim Wakefield | 5.48 | 2007 | ||
| 12 | Antonio Senzatela | 5.46 | 2019 | ||
| 13 | Carlos Torres | 5.44 | 2014 | ||
| 14 | C.C. Sabathia | 5.42 | 2014 | ||
| 15 | Chuck James | 5.29 | 2007 | ||
| 16 | Dallas Keuchel | 5.24 | 2019 | ||
| 17 | Chuck Finley | 5.12 | 2001 | ||
| 18 | Johnny Cueto | 5.12 | 2011 | ||
| 19 | Hideo Nomo | 5.05 | 2003 | ||
| 20 | Tim Wakefield | 5.05 | 2008 | ||
| 21 | Louie Varland | 4.98 | 2023 | ||
| 22 | Ted Lilly | 4.93 | 2005 | ||
| 23 | Hideo Nomo | 4.89 | 2002 | ||
| 24 | Ismael Valdes | 4.85 | 1997 | ||
| 25 | Gil Meche | 4.82 | 2007 | ||