Abstract: The field experiment was conducted to evaluate the agronomic and economic interference between cotton and pigeon pea at Students Farm, Sindh Agriculture University Tandojam, Pakistan. The intercropping pigeon pea with cotton showed adverse effects on all the growth and yield contributing parameters of cotton. In pigeon pea, the taller plants (300 cm), greater number of branches (12.33 plant-1), remarkably higher pods (223.66 plant-1), heavy seed index (103.33 g) and maximum seed yield (2182.33 kg ha-1) were observed in sole cropping system. In cotton, maximum plant height (164.00 cm), more production of bolls plant-1 (26.33), higher number of branches plant-1 (37.33), greater bolls plant-1 (16.66) and satisfactory seed cotton yield (2271 kg ha-1) were recorded when cotton was sown as sole crop. The agronomic parameters ob both intercrops decreased as compared to sole crops. The economic analysis indicated that cotton sole crop on an average recorded cost of production Rs. 31098 ha-1 against Rs. 26000 ha-1 intercropping of cotton with pigeon pea. The physical productivity study includes the total seed cotton yield of cotton as a sole crop and the total yield of cotton from intercropping with pigeon pea. The cotton sole crop yielded 2271.00 kg ha-1 and cotton intercropping with pigeon pea yielded 1120.00 kg ha-1. According to average per hectare revenue, productivity of cotton sole Rs. 56775.00 and intercropping cotton with pigeon pea Rs. 28000 ha-1. The cotton sole crop on average recorded net returns at the rate of Rs.25677 ha-1 whereas, cotton with pigeon pea intercropping exhibited the net returns at the rate of Rs. 2000 ha-1, which was very low due to adverse affect of pigeon pea intercropping with cotton. In this study input output ratio were determined to examine economic efficiency of both cotton sole and cotton intercropping with pigeon pea. The results derived from the above analysis reveal that growing cotton sole crop earned input output ratios at the proportion of 1:87 whereas, cotton intercropping with pigeon pea had input output ratio at the proportion 1:07. It was concluded that cotton-pigeon pea intercropping has adverse effects on each other, therefore the crops should be sown as sole crops.