A pot trial was conducted in the greenhouse of the National Research Centre, Dokki, Cairo, Egypt to study the effect of two levels of phosphorus P1 (1.44) and P2 (2.16) g P2O5 pot-1 and four Sulphur levels S0, S1, S2 and S3 at (0, 10, 15 and 20 g pot-1) on yield components of fababean, N and seed protein content as well as S-amino acid content (Methionine and Cysteine). The results showed that phosphorus and sulphur did not exhibit a significant effect on pod number however, seed number was decreased by P and S-treatments. Seed yield was increased at high P-level under S-levels, up to 15 g S pot-1, thereafter it declined. The best effect on both pod and seed weight was obtained by 10 and 15 g S pot-1 under the higher P-level. Further increase of S-addition (20 g pot-1) caused significant reductions in pod and seed yield to compare with those without S at higher P-level. The chemical composition of fababean revealed that N-concentrations generally increased by P and S additions, but crude protein content decreased with the highest application rate of S (20 g pot-1). S effects were more pronounced at the high P level than at the lower one. The maximum increase in Cysteine and Methionine contents due to S addition were respectively 17.6 and 24.6% expressed as % of dry matter and 11.11 and 27.8% expressed as )g/16 g N).The results showed a slight increase in phosphorus concentration by increasing S levels up to 15 g pot-1 at the two P levels .The beneficial effect was evident from the interaction between S and P indicating synergism of both nutrients which is explained by the individual responses to each element and it was greater than the unity (1.17 and 1.66). Such relation between both elements was pronounced under moderate (P1) or high (P2) which reflected on seed yield and achieving 17-66% increase. The results of the study highlight the importance of the combined S and P in improving yield and chemical constituents of fababean.