This study was conducted to assess water pollution by examining DNA fragmentation in selected fish organs (kidney, liver, gills, and muscle tissue) from Wallago attu, Sperata sarwari, Vulgaris vulgaris, and Labeo rohita collected from a known polluted section of the Chenab River, Pakistan, and from a control site. The fish were caught using a gill net and were assigned to three different weight groups (W1, W2, and W3) to study the degree of variation in DNA fragmentation in relation to body weight. In fish from the polluted site, DNA fragmentation was higher in kidney, liver, gills, and muscles, compared to the control. No significant DNA fragmentation was observed in fish collected from the control site. Highly significant (P < 0.01) relationship between body weight and DNA fragmentation was found in the organs of fish procured at the contaminated site. DNA fragmentation in body organs was found to be affected by the concentrations of lead, copper, nickel, and cadmium in W. attu, S. sarwari, L. rohita, and V. vulgarus harvested from Chenab River. DNA fragmentation in different freshwater fish species is therefore a reliable biomarker of water pollution. Resumo Este estudo foi conduzido para avaliar a poluição da água examinando a fragmentação do DNA em órgãos de peixes selecionados (rim, fígado, brânquias e tecido muscular) de Wallago attu, Sperata sarwari, Vulgaris vulgaris e Labeo rohita coletados de uma conhecida área poluída do rio Chenab, Paquistão e de um local de controle. Os peixes foram capturados usando uma rede branquial e foram divididos em três grupos de pesos diferentes (W1, W2 e W3) para estudar o grau de variação na fragmentação do DNA em relação ao peso corporal. Nos peixes do local poluído, a fragmentação do DNA foi maior nos rins, fígado, brânquias e músculos, em comparação ao controle. Não foi observada fragmentação significativa do DNA em peixes coletados no local de controle. Relação altamente significativa (P