The effect of soaking, autoclaving and toasting methods on the proximate and mineral composition and anti‐nutrients of lima (butter) bean (Phaseolus lunatus L.) was investigated. The raw seed showed high content of proteins, lipids and ash with good values of K, Ca, Mg, P, Na and Fe in comparison with other legumes. Potassium was the most abundant macro mineral while sodium was the least. Iron content was the highest among the micro minerals. Manganese was not detected in any of the samples. Raw lima bean contained cyanide, trypsin inhibitor, lectin, phytin and tannin. Phytate phosphorus was calculated to be 28.2% of total phosphorus. There was no significantly different (P > 0.05) in the crude protein content of raw and processed flour. There was significant difference (P < 0.05) in the values of the macro and micro mineral. Soaking, autoclaving and toasting completely eliminated trypsin inhibitor and lectin while it significantly (P < 0.05) reduced the levels of phytin, tannin and cyanide. Except for tannin autoclaving for 20 min was found to eliminate all the other anti‐nutrients in lima bean.