Field experiments were conducted in microplots to study the effect of N supply on competition between wheat and two prominent grassy weeds viz., Phalaris minor and Avena ludoviciana. Six treatments comprising three species combinations (wheat monoculture, weed monoculture, wheat and weed mixture in equal proportions) and two levels of N fertilization (20 and 120 kg/ha) were studied in a factorial randomized block design with four replications. Results revealed that total dry weight of wheat was significantly lower in mixture than in monoculture. Wheat was more competitive than P. minor at high N, but less competitive at low N.  A. ludoviciana, was more competitive than crop at both N levels. Wheat reduced photosynthesis of weeds to a greater extent as compared to pure weed population. A. ludoviciana exhibited higher values of Pn as compared to P. minor at both N levels in both stand (monoculture and mixture) types. Leaf area index and leaf chlorophyll content of both wheat and weed were at par in mixture at high N and in monoculture at low N, indicating a higher competitiveness (for nitrogen) of A. ludoviciana.