This study evaluated the effects of dietary replacement of soyabean meal (SBM) with yellow lupine seed meal (YLM) in turkeys. A total of 1120 one-day-old Hybrid Converter female turkeys were fed diets containing 0%, 8%, 16% and 24% of YLM (LM₀, LM₈, LM₁₆, LM₂₄, respectively) in a 16-week experiment. In the first phase of feeding (weeks 0–4), an increase in the YLM content of diets caused a linear decrease in feed intake (FI) and body weight gain (BWG) and the noted differences were significant (P < 0.001) in group LM₂₄. In 16-week-old turkeys, dietary inclusion of lupine at up to 24% had no adverse effects on FI, BWG or feed conversion. Experimental diets had no influence on the analysed serum parameters or mortality of turkeys or on the incidence of footpad dermatitis. No significant changes in carcass and muscle yields were observed. Group LM₂₄ turkeys were characterized by significantly (P = 0.033 vs LM0) higher relative gizzard tissue weight. The abdominal fat content tended to increase (P = 0.055 vs LM₀) in birds fed lupine-based diets. A linear increase (P < 0.001) in the concentrations of polyunsaturated fatty acids was noted in meat from turkeys fed lupine-based diets; this did not change the n-6/n-3 PUFA ratio, but improved the values of the atherogenic and thrombogenic indices. Diets containing YLM had no influence on the chemical composition, physicochemical properties or sensory attributes of turkey meat. In conclusion, starter diets containing 24% YLM could have an adverse influence on bird performance. Yellow lupine seeds can be added to diets for older turkeys at up to 24% as an effective substitute for SBM without affecting the key variables of performance and without negative effects on meat quality.