Pomegranate peels are an industrial by-product high in sugar and phytochemical content and pose an environmental concern. Meanwhile, ensiling legume forage such as berseem is difficult due to its lower dry matter content and water-soluble carbohydrate-to-buffering capacity ratio, which leads to a poor fermentation process. To date, no studies have been conducted to investigate the effect of co-ensiling pomegranate peels with berseem. Thus, silage quality was evaluated after co-ensiling of berseem (control) with 50, 100, and 200 g/kg pomegranate peels or 50 g/kg molasses for 0, 15, 30, and 45 days (Experiment 1). Further, rumen nutrient degradation, methane production, and rumen fermentation parameters were evaluated in vitro (Experiment 2). Pomegranate peels (200 g/kg) and molasses reduced silage pH compared to control (4.41 or 3.79 vs. 5.02), ammonia-N (2.66 or 3.14 vs. 13.39 g/kg N), and butyric acid (0.05 or 0.1 vs. 0.96 g/kg DM) however, dry matter (323.5 or 283.6 vs. 212.8) and non-fiber carbohydrates (264.8 or 351.8 vs.136.9 g/kg) were increased, respectively. Pomegranate peels and molasses significantly (P < 0.05) increased rumen nutrient degradation and significantly (P < 0.05) decreased methane and ammonia-N production (Experiment 2). The chemical composition of silage, in-vitro rumen fermentation, and silage quality parameters were significantly (P < 0.05) correlated. Pomegranate peels and molasses have potentially improved silage quality and positively influenced rumen fermentation parameters.