Between October 3, 2005 and October 3, 2025, 11 pitchers are tied for the best ERA for the Giants, with an ERA of 0.00. The first three are Christian Koss, Andrew Vasquez and David Villar.

	NAME	ERA	G	W	L	W%	GS	SO	CG	SHO	SV	IP	H	ER	R	HR	BB	HBP	GF	IBB	TBF	WP	K/9	BB/9	K/BB	HR/9	K%	BB%	WHIP	BABIP	RA	H/9
1	Christian Koss C. Koss	0.00	4	0	0		0	0	0	0	0	4.0	4	0	0	0	0	0	4	0	16	0	0.00	0.00		0.00	0.0	0.0	1.00	.250	0.00	9.00
2	Andrew Vasquez A. Vasquez	0.00	1	0	0		0	4	0	0	0	2.0	0	0	0	0	1	0	0	0	7	0	18.00	4.50	4.00	0.00	57.1	14.3	0.50	.000	0.00	0.00
3	David Villar D. Villar	0.00	1	0	0		0	0	0	0	0	1.0	0	0	0	0	1	0	1	0	3	0	0.00	9.00	0.00	0.00	0.0	33.3	1.00	.000	0.00	0.00
4	Tyler Heineman T. Heineman	0.00	1	0	0		0	0	0	0	0	1.0	1	0	0	0	0	0	1	0	3	0	0.00	0.00		0.00	0.0	0.0	1.00	.333	0.00	9.00
5	Chase d'Arnaud C. d'Arnaud	0.00	1	0	0		0	0	0	0	0	1.0	1	0	0	0	0	0	1	0	4	0	0.00	0.00		0.00	0.0	0.0	1.00	.250	0.00	9.00
6	Dan Slania D. Slania	0.00	1	0	0		0	0	0	0	0	1.0	0	0	0	0	0	0	1	0	3	0	0.00	0.00		0.00	0.0	0.0	0.00	.000	0.00	0.00
7	Austin Slater A. Slater	0.00	1	0	0		0	0	0	0	0	0.1	0	0	0	0	1	0	1	0	2	0	0.00	27.00	0.00	0.00	0.0	50.0	3.00	.000	0.00	0.00
8	Joe Nathan J. Nathan	0.00	7	1	0	1.000	0	5	0	0	0	4.1	3	0	0	0	2	0	1	0	18	1	10.38	4.15	2.50	0.00	27.8	11.1	1.15	.273	0.00	6.23
9	Heath Hembree H. Hembree	0.00	9	0	0		0	12	0	0	0	7.2	4	0	0	0	2	0	2	0	29	0	14.09	2.35	6.00	0.00	41.4	6.9	0.78	.267	0.00	4.70
10	Brandon Crawford B. Crawford	0.00	1	0	0		0	0	0	0	0	1.0	1	0	0	0	1	0	1	0	5	0	0.00	9.00	0.00	0.00	0.0	20.0	2.00	.250	0.00	9.00
11	Pablo Sandoval P. Sandoval	0.00	2	0	0		0	0	0	0	0	2.0	0	0	0	0	0	1	2	0	6	0	0.00	0.00		0.00	0.0	0.0	0.00	.000	0.00	0.00
12	Luis F. Ortiz L. F. Ortiz	1.04	6	0	0		0	6	0	0	0	8.2	5	1	1	0	3	0	4	0	33	0	6.23	3.12	2.00	0.00	18.2	9.1	0.92	.208	1.04	5.19
13	Trevor McDonald T. McDonald	1.50	4	1	0	1.000	2	15	0	0	0	18.0	13	3	6	1	3	0	1	0	70	1	7.50	1.50	5.00	0.50	21.4	4.3	0.89	.235	3.00	6.50
14	Nick Tropeano N. Tropeano	1.50	4	1	0	1.000	0	2	0	0	0	6.0	4	1	2	0	2	0	1	0	23	1	3.00	3.00	1.00	0.00	8.7	8.7	1.00	.211	3.00	6.00
15	Erik Cordier E. Cordier	1.50	7	0	0		0	9	0	0	0	6.0	5	1	4	0	2	3	2	0	28	1	13.50	3.00	4.50	0.00	32.1	7.1	1.17	.357	6.00	7.50
16	Austin Warren A. Warren	1.69	6	0	0		0	7	0	0	0	10.2	9	2	2	1	5	0	3	0	42	0	5.91	4.22	1.40	0.84	16.7	11.9	1.31	.276	1.69	7.59
17	Thomas Szapucki T. Szapucki	1.98	10	0	0		0	16	0	0	0	13.2	12	3	3	2	4	0	2	0	54	1	10.54	2.63	4.00	1.32	29.6	7.4	1.17	.313	1.98	7.90
18	Burch Smith B. Smith	2.08	10	0	0		0	6	0	0	0	8.2	10	2	3	0	4	0	2	0	41	0	6.23	4.15	1.50	0.00	14.6	9.8	1.62	.323	3.12	10.38
19	Kyle Barraclough K. Barraclough	2.25	10	0	0		0	10	0	0	0	8.0	5	2	3	1	9	0	3	0	40	1	11.25	10.13	1.11	1.13	25.0	22.5	1.75	.200	3.38	5.63
20	Alex Young A. Young	2.39	24	1	1	.500	1	20	0	0	0	26.1	28	7	11	0	11	1	1	0	114	3	6.84	3.76	1.82	0.00	17.5	9.6	1.48	.341	3.76	9.57
21	Santiago Casilla S. Casilla	2.42	414	32	22	.593	0	366	0	0	123	394.2	303	106	118	30	155	20	212	21	1,619	32	8.35	3.53	2.36	0.68	22.6	9.6	1.16	.260	2.69	6.91
22	Joel Peguero J. Peguero	2.42	17	3	1	.750	0	17	0	0	0	22.1	15	6	7	2	8	0	4	1	86	0	6.85	3.22	2.13	0.81	19.8	9.3	1.03	.220	2.82	6.04
23	Javier Lopez J. Lopez	2.47	446	17	8	.680	0	184	0	0	10	251.0	194	69	77	8	104	7	88	23	1,037	6	6.60	3.73	1.77	0.29	17.7	10.0	1.19	.253	2.76	6.96
24	Ramon E Ramirez R. E Ramirez	2.58	97	4	3	.571	0	81	0	0	5	101.1	76	29	35	6	42	3	29	6	417	8	7.19	3.73	1.93	0.53	19.4	10.1	1.16	.246	3.11	6.75
25	Sergio Romo S. Romo	2.58	515	32	26	.552	0	498	0	0	84	439.2	331	126	136	39	89	17	187	13	1,737	12	10.19	1.82	5.60	0.80	28.7	5.1	0.96	.267	2.78	6.78