This study investigated the effects of feeding cotton gin trash (CGT) to Mecheri ram lambs, as an alternate diet, on growth performance, carcass characteristics, and meat quality. A growth performance trial was conducted with thirty-two weaned Mecheri ram lambs with an average body weight of 12.64 ± 0.74 kg, which were assigned to four groups (n = eight animals in each group). The diet’s roughage part was replaced by CGT at percentages of 0% (T1), 25% (T2), 50% (T3), and 75% (T4). The growth trial lasted six months (180 days) from weaning lambs at 3–4 months until 9 months for marketing. All the animals were fed on a dry matter requirement basis at 4% of their body weight. The study revealed that the lambs fed with 50 (T3) and 75 (T4) % inclusion levels of CGT showed significantly (p < 0.01) higher total body weight gain than the T1 and T2 groups. The average daily gain of lambs in T3 (99.24 g) and T4 (105.51 g) were significantly (p < 0.01) higher than T1 (80.77 g) and T2 (83.61 g) groups. Throughout the study period, there was no statistically significant (p > 0.05) difference in the average Dry Matter Intake (DMI) (g) between the groups; however, the lambs in T4 demonstrated higher feed efficiency (7.4) than the T1 (9.3) group. The slaughter studies revealed that the lambs in the T4 followed by the T3 groups registered significantly (p < 0.01) higher hot carcass weight, dressing percentage, and meat: bone ratio than T2 and T1 group animals. The T3 and T4 groups had significantly (p < 0.05) higher weights of the liver, spleen, head, stomach, and empty intestines when compared to T1 and T2 groups; however, there was no significant (p > 0.05) difference in the weights of edible and inedible offals. In addition, there were no significant variations (p > 0.05) in pH, WHC, shear force value, sensory characteristics, and proximate composition of meat among treatment groups. The SFA levels in the T3, T4, and T2 groups were substantially (p < 0.01) greater than in the control group (T1). In contrast, the proportion of MUFA in the T1 group was significantly (p < 0.05) greater than in the T3 and T4 treatment groups. There was no significant difference in PUFA or the PUFA/SFA ratio between the treatment groups. In accordance with current research findings, the CGT can be added up to 75% of the roughage component in sheep feed as an effective unconventional supplementation, as it improves body weight, feed efficiency, and carcass characteristics in Mecheri ram lambs.