Heat stress can adversely affect the rumen environment and the growth performance of goats. The present study aimed to investigate the effects of Saccharomyces cerevisiae (SC), Clostridium butyricum (CB), and their mixture on B-vitamin production in the rumen and the growth performance of heat-stressed goats. Firstly, twelve Macheng × Boer crossed goats (24.21 ± 2.05 kg, control) were modeled to become heat-stressed goats (HS1). Then, the B-vitamin concentrations in the rumen and the parameters of growth performance were measured in goats. The results showed that heat stress could cause significantly decreased vitamin B1, B2, B6, B12, and niacin concentrations (p < 0.05). It also could cause a significantly reduced dry matter (DM) intake (DMI) and average daily gain (ADG) (p < 0.05). However, the digestibilities of DM, neutral detergent fiber (NDF), and acid detergent fiber (ADF) were significantly increased (p < 0.05) in HS1 compared to controls. Then, these twelve heat-stressed goats were divided equally into four groups: control group (HS2, no probiotic supplemented), SC group (0.30% SC supplemented to the basal diet), CB group (0.05% CB supplemented to the basal diet), and mix group (0.30% SC and 0.05% CB supplemented to the basal diet). They were used in a 4 × 4 Latin square experimental design. The results showed that the concentrations of vitamins B1, B2, and niacin in the rumen and the DMI, ADG, and the digestibility of DM, NDF, and ADF were significantly increased (p < 0.05) with SC, CB, and their mixture supplementation (p < 0.05). These results suggest that dietary supplementation with SC and CB could improve B-vitamin production in the rumen and the growth performance of heat-stressed goats.