Infant botulism is the most common form of human botulism in Argentina and the United States. BabyBIG (botulism immune globulin intravenous [human]) is the antitoxin of choice for specific treatment of infant botulism in the United States. However, its high cost limits its use in many countries. We report here the effectiveness and safety of equine botulinum antitoxin (EqBA) as an alternative treatment. We conducted an analytical, observational, retrospective, and longitudinal study on cases of infant botulism registered in Mendoza, Argentina, from 1993 to 2007. We analyzed 92 medical records of laboratory-confirmed cases and evaluated the safety and efficacy of treatment with EqBA. Forty-nine laboratory-confirmed cases of infant botulism demanding admission in intensive care units and mechanical ventilation included 31 treated with EqBA within the 5 days after the onset of signs and 18 untreated with EqBA. EqBA-treated patients had a reduction in the mean length of hospital stay of 23.9 days (P = 0.0007). For infants treated with EqBA, the intensive care unit stay was shortened by 11.2 days (P = 0.0036), mechanical ventilation was reduced by 11.1 days (P = 0.0155), and tube feeding was reduced by 24.4 days (P = 0.0001). The incidence of sepsis in EqBA-treated patients was 47.3% lower (P = 0.0017) than in the untreated ones. Neither sequelae nor adverse effects attributable to EqBA were noticed, except for one infant who developed a transient erythematous rash. These results suggest that prompt treatment of infant botulism with EqBA is safe and effective and that EqBA could be considered an alternative specific treatment for infant botulism when BabyBIG is not available.