Ambrose Puttmann had the lowest ERA with an ERA worse than 0.00 in 1903, with an ERA of 0.95 in his rookie season.

	NAME	ERA	SEASON	TM	G	W	L	W%	GS	SO	CG	SHO	SV	IP	H	ER	R	HR	BB	HBP	GF	TBF	WP	K/9	BB/9	K/BB	HR/9	K%	BB%	WHIP	BABIP	RA	ERA-	FIP	FIP-	H/9	PRAA
1	Ambrose Puttmann A. Puttmann	0.95	1903	NYH	3	2	0	1.000	2	8	1	0	0	19.0	16	2	9	0	4	1	1	75	1	3.79	1.89	2.00	0.00	10.7	5.3	1.05	.258	4.26	30	2.70	85	7.58	1.1
2	Martin Glendon M. Glendon	0.98	1903	CLE	3	1	2	.333	3	9	3	0	0	27.2	20	3	9	0	7	0	0	106	0	2.93	2.28	1.29	0.00	8.5	6.6	0.98	.222	2.93	34	2.86	99	6.51	0
3	Red Ames R. Ames	1.29	1903	NYG	2	2	0	1.000	2	14	2	1	0	14.0	5	2	2	0	8	0	0	52	0	9.00	5.14	1.75	0.00	26.9	15.4	0.93	.167	1.29	40	2.47	76	3.21	1.2
4	Earl Moore E. Moore	1.74	1903	CLE	29	20	8	.714	27	148	27	3	0	247.2	196	48	88	0	62	5	2	969	8	5.38	2.25	2.39	0.00	15.3	6.4	1.04	.260	3.20	60	2.37	82	7.12	13.5
5	Stan Yerkes S. Yerkes	1.80	1903	SLN	1	0	1	.000	1	3	0	0	0	5.0	8	1	6	0	0	0	0	24	0	5.40	0.00		0.00	12.5	0.0	1.60	.381	10.80	56	1.55	48	14.40	0.9
6	Jesse Stovall J. Stovall	2.05	1903	CLE	6	5	1	.833	6	12	6	2	0	57.0	44	13	17	0	21	3	0	231	1	1.89	3.32	0.57	0.00	5.2	9.1	1.14	.226	2.68	71	3.60	125	6.95	-4.8
7	Sam Leever S. Leever	2.06	1903	PIT	36	25	7	.781	34	90	30	7	1	284.1	255	65	98	2	60	5	2	1,135	6	2.85	1.90	1.50	0.06	7.9	5.3	1.11	.259	3.10	63	2.90	88	8.07	12.2
8	Cy Young C. Young	2.08	1903	BSA	40	28	9	.757	35	176	34	7	2	341.2	294	79	115	6	37	9	5	1,314	5	4.64	0.97	4.76	0.16	13.4	2.8	0.97	.265	3.03	70	2.35	80	7.74	22.2
9	Bill Bernhard B. Bernhard	2.12	1903	CLE	20	14	5	.737	19	60	18	3	0	165.2	151	39	62	1	21	0	1	644	2	3.26	1.14	2.86	0.05	9.3	3.3	1.04	.267	3.37	73	2.49	86	8.20	6.8
10	Doc White D. White	2.13	1903	CWS	37	17	16	.515	36	114	29	3	0	300.0	258	71	119	4	69	14	1	1,197	7	3.42	2.07	1.65	0.12	9.5	5.8	1.09	.255	3.57	76	3.00	107	7.74	-9.7
11	Addie Joss A. Joss	2.19	1903	CLE	32	18	13	.581	31	120	31	3	0	283.2	232	69	105	3	37	9	1	1,087	5	3.81	1.17	3.24	0.10	11.0	3.4	0.95	.249	3.33	75	2.53	88	7.36	10.3
12	George Mullin G. Mullin	2.25	1903	DET	41	19	15	.559	36	170	31	6	2	320.2	284	80	128	4	106	8	5	1,312	6	4.77	2.98	1.60	0.11	13.0	8.1	1.22	.273	3.59	75	2.92	98	7.97	2.1
13	George Merritt G. Merritt	2.25	1903	PIT	1	0	0		0	2	0	0	0	4.0	4	1	3	0	1	0	1	16	0	4.50	2.25	2.00	0.00	12.5	6.3	1.25	.308	6.75	69	2.50	76	9.00	0.3
14	Larry Milton L. Milton	2.25	1903	SLN	1	0	0		0	0	0	0	0	4.0	3	1	1	0	1	0	1	16	0	0.00	2.25	0.00	0.00	0.0	6.3	1.00	.200	2.25	70	3.50	109	6.75	-0.1
15	Lave Winham L. Winham	2.25	1903	PIT	5	3	1	.750	4	22	3	1	0	36.0	33	9	20	0	21	0	1	164	3	5.50	5.25	1.05	0.00	13.4	12.8	1.50	.273	5.00	69	3.28	100	8.25	0
16	Bill Dinneen B. Dinneen	2.26	1903	BSA	37	21	13	.618	34	148	32	6	2	299.0	255	75	98	6	66	4	3	1,178	5	4.45	1.99	2.24	0.18	12.6	5.6	1.07	.261	2.95	76	2.73	93	7.68	7.1
17	Christy Mathewson C. Mathewson	2.26	1903	NYG	45	30	13	.698	42	267	37	3	2	366.1	321	92	136	4	100	10	3	1,502	18	6.56	2.46	2.67	0.10	17.8	6.7	1.15	.283	3.34	70	2.34	72	7.89	37
18	Willie Sudhoff W. Sudhoff	2.27	1903	SLA	38	21	15	.583	35	104	30	5	0	293.2	262	74	100	4	56	9	3	1,164	5	3.19	1.72	1.86	0.12	8.9	4.8	1.08	.260	3.06	80	2.89	102	8.03	-4.1
19	Bill Donovan B. Donovan	2.29	1903	DET	35	17	16	.515	34	187	34	4	0	307.0	247	78	104	3	95	5	1	1,223	7	5.48	2.79	1.97	0.09	15.3	7.8	1.11	.262	3.05	76	2.64	89	7.24	11.6
20	Jake Weimer J. Weimer	2.30	1903	CHC	35	20	8	.714	33	128	27	3	0	282.0	241	72	111	4	104	11	2	1,184	5	4.09	3.32	1.23	0.13	10.8	8.8	1.22	.253	3.54	72	3.25	101	7.69	-2
21	Eddie Plank E. Plank	2.38	1903	PHA	43	23	16	.590	40	176	33	3	0	336.0	317	89	128	5	65	23	2	1,363	8	4.71	1.74	2.71	0.13	12.9	4.8	1.14	.285	3.43	78	2.68	89	8.49	13.9
22	Barney Pelty B. Pelty	2.40	1903	SLA	7	3	3	.500	6	20	5	0	1	48.2	49	13	25	1	15	2	1	205	0	3.70	2.77	1.33	0.18	9.8	7.3	1.32	.287	4.62	85	3.25	115	9.06	-2.7
23	Joe McGinnity J. McGinnity	2.43	1903	NYG	55	31	20	.608	48	171	44	3	2	434.0	391	117	162	4	109	19	6	1,786	5	3.55	2.26	1.57	0.08	9.6	6.1	1.15	.261	3.36	75	2.97	91	8.11	13
24	Deacon Phillippe D. Phillippe	2.43	1903	PIT	36	25	9	.735	33	123	31	4	2	289.1	269	78	116	4	29	4	3	1,150	5	3.83	0.90	4.24	0.12	10.7	2.5	1.03	.268	3.61	74	2.42	74	8.37	27.6
25	Rube Waddell R. Waddell	2.44	1903	PHA	39	21	16	.568	38	302	34	4	0	324.0	274	88	109	3	85	8	1	1,291	9	8.39	2.36	3.55	0.08	23.4	6.6	1.11	.303	3.03	80	1.87	62	7.61	41.9