I didn't find anything for this season, but the Chicago White Sox had the worst record by a team before the All-Star Game in 2024, with a record of 27-71.

Interpreted as:

worst record before MLB all star break this season

	TEAM	REC	SEASON	W%	G	W	L	AB	R	H	2B	3B	HR	RBI	BB	HBP	SO	SB	CS	PA	TB	XBH	SH	SF	IBB	GIDP	AVG	OBP	SLG	OPS
1	White Sox	27-71	2024	.276	98	27	71	3,237	313	713	145	5	85	298	256	29	843	63	14	3,553	1,123	235	14	17	6	78	.220	.282	.347	.629
2	Marlins	33-63	2024	.344	96	33	63	3,252	336	760	133	12	78	327	205	30	798	52	27	3,516	1,151	223	11	18	11	77	.234	.284	.354	.638
3	Rockies	34-63	2024	.351	97	34	63	3,286	403	801	168	15	104	385	269	32	927	53	19	3,627	1,311	287	13	27	12	83	.244	.305	.399	.704
4	Athletics	37-61	2024	.378	98	37	61	3,265	390	740	137	12	122	376	307	35	949	53	14	3,642	1,267	271	13	22	8	60	.227	.298	.388	.686
5	Angels	41-55	2024	.427	96	41	55	3,181	385	747	144	10	101	358	277	43	803	80	34	3,529	1,214	255	7	21	3	65	.235	.303	.382	.685
6	Nationals	44-53	2024	.454	97	44	53	3,211	402	768	158	10	80	378	280	52	747	126	47	3,585	1,186	248	14	28	7	66	.239	.308	.369	.677
7	Blue Jays	45-52	2024	.464	97	45	52	3,197	394	754	161	13	87	374	317	42	714	45	9	3,594	1,202	261	10	28	5	83	.236	.311	.376	.687
8	Rangers	46-50	2024	.479	96	46	50	3,237	414	779	131	11	101	397	304	35	745	52	14	3,599	1,235	243	4	19	14	65	.241	.311	.382	.693
9	Cubs	47-51	2024	.480	98	47	51	3,265	415	768	147	16	100	391	327	52	865	78	19	3,678	1,247	263	9	25	10	55	.235	.313	.382	.695
10	Reds	47-50	2024	.485	97	47	50	3,169	432	732	158	20	108	406	298	55	872	134	29	3,560	1,254	286	12	26	5	52	.231	.306	.396	.702
11	Giants	47-50	2024	.485	97	47	50	3,277	427	801	164	14	96	408	320	31	809	31	14	3,668	1,281	274	7	33	11	69	.244	.315	.391	.706
12	Tigers	47-50	2024	.485	97	47	50	3,262	413	763	142	31	99	397	278	38	835	44	14	3,606	1,264	272	3	25	7	55	.234	.299	.387	.687
13	Pirates	48-48	2024	.500	96	48	48	3,253	402	751	132	11	99	389	301	31	886	49	10	3,629	1,202	242	12	32	9	63	.231	.299	.370	.669
14	Rays	48-48	2024	.500	96	48	48	3,199	376	754	150	11	86	350	311	49	862	95	35	3,587	1,184	247	8	20	6	63	.236	.311	.370	.681
15	Padres	50-49	2024	.505	99	50	49	3,355	448	876	143	11	109	432	276	30	662	69	19	3,690	1,368	263	14	15	12	88	.261	.322	.408	.729
16	Diamondbacks	49-48	2024	.505	97	49	48	3,280	482	833	167	19	102	461	324	46	763	59	16	3,706	1,344	288	17	39	12	67	.254	.326	.410	.736
17	Mets	49-46	2024	.516	95	49	46	3,275	465	818	176	9	121	447	306	50	769	69	15	3,655	1,375	306	8	16	7	65	.250	.322	.420	.742
18	Cardinals	50-46	2024	.521	96	50	46	3,257	398	799	149	11	94	374	279	39	807	56	16	3,620	1,252	254	14	31	5	44	.245	.310	.384	.694
19	Astros	50-46	2024	.521	96	50	46	3,302	457	866	162	11	110	440	267	39	669	64	16	3,644	1,380	283	6	30	11	72	.262	.322	.418	.740
20	Mariners	52-46	2024	.531	98	52	46	3,203	379	701	129	10	109	362	319	58	1,013	74	18	3,602	1,177	248	7	15	6	62	.219	.300	.367	.667
21	Royals	52-45	2024	.536	97	52	45	3,218	442	795	160	24	101	429	257	29	664	80	18	3,550	1,306	285	13	33	14	57	.247	.306	.406	.711
22	Red Sox	53-43	2024	.552	96	53	43	3,301	447	838	175	24	113	430	299	43	930	88	29	3,674	1,400	312	6	25	18	51	.254	.322	.424	.746
23	Braves	53-42	2024	.558	95	53	42	3,205	407	774	178	9	109	386	266	35	844	44	13	3,534	1,297	296	2	26	6	60	.241	.304	.405	.709
24	Twins	54-42	2024	.563	96	54	42	3,257	466	827	192	15	115	443	279	68	757	46	18	3,639	1,394	322	5	30	7	77	.254	.323	.428	.751
25	Brewers	55-42	2024	.567	97	55	42	3,296	466	839	153	15	99	442	363	32	849	133	24	3,714	1,319	267	6	17	8	61	.255	.333	.400	.733