| Career - Worst ERA | |||
| Rk | Player Name | Totals | |
| 1 | C.C. Sabathia | 5.19 | |
| 2 | Jose DeJesus | 5.17 | |
| 3 | Pete Harnisch | 4.91 | |
| 4 | Greg Swindell | 4.91 | |
| 5 | Kevin Gausman | 4.73 | |
| 6 | Robbie Ray | 4.71 | |
| 7 | Derek Lowe | 4.56 | |
| 8 | Gil Heredia | 4.53 | |
| 9 | Andy Pettitte | 4.46 | |
| 10 | Julio Urias | 4.40 | |
| 11 | Ted Lilly | 4.38 | |
| 12 | Ian Kennedy | 4.35 | |
| 13 | Jamie Moyer | 4.16 | |
| 14 | Mark Buehrle | 4.08 | |
| 15 | David Cone | 3.78 | |
| 16 | Jeff Fassero | 3.62 | |
| 17 | Jon Gray | 3.59 | |
| 18 | Anibal Sanchez | 3.53 | |
| 19 | Chris Haney | 3.40 | |
| 20 | Roy Halladay | 3.22 | |
| 21 | Chris Sale | 3.22 | |
| 22 | Edwin Diaz | 3.05 | |
| 23 | Kenley Jansen | 2.93 | |
| 24 | Jonathan Papelbon | 2.34 | |
| Single Season - Worst ERA | |||||
| Rk | Player Name | Totals | Year | ||
| 1 | Martin Perez | 6.82 | 2020 | ||
| 2 | Jose DeJesus | 6.52 | 1991 | ||
| 3 | Gil Heredia | 5.76 | 2001 | ||
| 4 | C.C. Sabathia | 5.73 | 2002 | ||
| 5 | Jake Arrieta | 5.71 | 2020 | ||
| 6 | Ted Lilly | 5.68 | 2009 | ||
| 7 | Kevin Gausman | 5.52 | 2024 | ||
| 8 | Julio Urias | 5.43 | 2023 | ||
| 9 | Reynaldo Lopez | 5.29 | 2018 | ||
| 10 | Kyle Lohse | 5.18 | 2013 | ||
| 11 | Kevin Gausman | 5.16 | 2019 | ||
| 12 | Josh Tomlin | 5.12 | 2012 | ||
| 13 | Jamie Moyer | 5.11 | 2002 | ||
| 14 | Matt Clement | 5.08 | 2001 | ||
| 15 | Tim Redding | 5.04 | 2004 | ||
| 16 | Lance Lynn | 5.03 | 2013 | ||
| 17 | Greg Swindell | 4.96 | 1994 | ||
| 18 | C.C. Sabathia | 4.93 | 2003 | ||
| 19 | Pete Harnisch | 4.93 | 1999 | ||
| 20 | Bobby Miller | 4.93 | 2024 | ||
| 21 | Oil Can Boyd | 4.88 | 1991 | ||
| 22 | Jamie Moyer | 4.86 | 1995 | ||
| 23 | Tyler Skaggs | 4.86 | 2019 | ||
| 24 | Tom Glavine | 4.84 | 1990 | ||
| 25 | Kevin Gausman | 4.79 | 2018 | ||