| Career - Worst ERA | |||
| Rk | Player Name | Totals | |
| 1 | Jeff Suppan | 5.08 | |
| 2 | John Burkett | 5.00 | |
| 3 | Andy Pettitte | 5.00 | |
| 4 | David Wells | 4.91 | |
| 5 | Mike Boddicker | 4.81 | |
| 6 | Tom Glavine | 4.71 | |
| 7 | Domingo German | 4.68 | |
| 8 | Livan Hernandez | 4.58 | |
| 9 | Scott Baker | 4.58 | |
| 10 | Kenta Maeda | 4.50 | |
| 11 | Cristian Javier | 4.50 | |
| 12 | Tom Koehler | 4.47 | |
| 13 | Colby Lewis | 4.42 | |
| 14 | Barry Zito | 4.23 | |
| 15 | Marcus Stroman | 4.19 | |
| 16 | Tommy Greene | 4.15 | |
| 17 | Jason Isringhausen | 4.00 | |
| 18 | Mike Mussina | 3.99 | |
| 19 | Yu Darvish | 3.94 | |
| 20 | Bruce Hurst | 3.85 | |
| 21 | Dinelson Lamet | 3.83 | |
| 22 | Dwight Gooden | 3.56 | |
| 23 | Darryl Kile | 3.53 | |
| 24 | Koji Uehara | 2.45 | |
| Single Season - Worst ERA | |||||
| Rk | Player Name | Totals | Year | ||
| 1 | Mark Leiter | 6.90 | 1997 | ||
| 2 | Tom Glavine | 6.72 | 1991 | ||
| 3 | Juan Guzman | 6.45 | 1994 | ||
| 4 | Mike Fiers | 6.45 | 2021 | ||
| 5 | Andy Pettitte | 6.18 | 2007 | ||
| 6 | Braden Looper | 6.08 | 2009 | ||
| 7 | Allen Watson | 5.91 | 1998 | ||
| 8 | Livan Hernandez | 5.80 | 1999 | ||
| 9 | Ariel Miranda | 5.79 | 2017 | ||
| 10 | Tim Adleman | 5.69 | 2017 | ||
| 11 | John Burkett | 5.63 | 1997 | ||
| 12 | Bronson Arroyo | 5.63 | 2013 | ||
| 13 | Horacio Ramirez | 5.62 | 2004 | ||
| 14 | John Doherty | 5.61 | 1994 | ||
| 15 | Scott Baker | 5.56 | 2011 | ||
| 16 | John Lackey | 5.31 | 2018 | ||
| 17 | Bronson Arroyo | 5.29 | 2014 | ||
| 18 | Tom Glavine | 5.24 | 2004 | ||
| 19 | Mike Pelfrey | 5.22 | 2009 | ||
| 20 | Cristian Javier | 5.14 | 2022 | ||
| 21 | Kirk Rueter | 5.12 | 2003 | ||
| 22 | Jerome Williams | 5.12 | 2006 | ||
| 23 | Hisashi Iwakuma | 5.10 | 2017 | ||
| 24 | Jeff Suppan | 5.08 | 2004 | ||
| 25 | John Burkett | 5.06 | 1998 | ||