Background Ferrum phosphoricum (FP) has been used by traditional medicine practitioners for various ailments since ancient times. However, scientific evidence on the safety of FP is still unavailable. Thus, the current study aimed to investigate the acute and sub-acute oral toxicity of homeopathic FP in experimental rats. Methods In an acute toxicity investigation, a single dose of 2,000 µL/kg of FP 6c, 30c and 200c was administered to female Wistar rats, which were monitored for up to 14 days according to the Organization for Economic Cooperation and Development (OECD) guideline 423. For a sub-acute toxicity study, FP 6c, 30c and 200c (200 µL/kg) were administered to male and female rats for 28 days as per the OECD guideline 407. All the animals were observed for mortality, clinical signs and body weight during the study. At the end of the experiment, hematological, biochemical and histopathological assessments were performed. Results During the acute toxicity study, no mortality was observed in rats administered with FP, and thus the median lethal dose (LD50) was identified as >2,000 µL/kg. In the sub-acute study, no mortality or adverse clinical signs were noticed with FP treatment. Moreover, weekly body weight gain was normal. Hematological and biochemical investigations revealed no abnormalities. Furthermore, histological analysis of FP-treated rats’ vital organs revealed no pathological changes. Conclusion Overall, our findings imply that FP 6c, 30c and 200c potencies are safe and do not cause toxicity when given orally to Wistar albino rats for an extended period at a dose of 200 µL/kg.