Weed competition is one of the most important production constraints causing up to 91.6% reduction in potential yield of cowpea. Therefore, an experiment was conducted at Sirinka and at Jari, northern Ethiopia, during the 2014 main cropping season: to evaluate the effect of planting pattern and frequency of weeding on weeds, yield components and yield of cowpea. There were 18 treatments comprising combination of three planting patterns (S1: 60 cm x 10 cm, S2: 45 cm x 15 cm, S3: 45 cm x 10 cm) and six weeding frequencies viz. one hand weeding and hoeing at 2 weeks after crop emergence (WAE), one hand weeding and hoeing at 3 WAE, one hand weeding and hoeing at 4 WAE, two hand weeding and hoeing at 2 and 5 WAE, weed free check, and weedy check. The treatments were arranged in factorial combination in a randomized complete block design with three replications. Results showed significantly lower total weed dry weight at Sirinka than at Jari. The highest weed control efficacy was recorded in two hand weeding and hoeing at 2 and 5 WAE of cowpea at Sirinka. The plants in weedy check plots at Jari attained maximum height which was significantly higher than all the other treatments. Significantly highest number of pods per plant was recorded in weed free check under 60 cm x 10 cm spacing at Jari. Number of seeds per pod was highest in weed free check at 45 cm x 10 cm spacing at Sirinka. The interaction of weeding frequency and location had significant effect on cowpea dry biomass yield. The highest total dry biomass (12413 kg ha<sup>-1</sup>) was obtained in one hand weeding and hoeing at 4 WAE at Jari while the highest grain yield (4508 kg ha<sup>-1</sup>) was recorded from complete weed free under 60 cm x 10 cm spacing at Sirinka. The harvest index ranged from 18.2% in weedy check at Jari to 39.1% in weed free check at Sirinka. The results indicated that the use of 60 cm x 10 cm planting pattern in combination with hand weeding and hoeing at 3 WAE at Sirinka and hand weeding and hoeing at 4 WAE at Jari proved to be the most feasible practice.