The ecological factors of aquatic environments are changing because of global climate change, which can directly or indirectly influence the expression of different phenotypic traits in many organisms. The present study was conducted under laboratory conditions to unveil the effects of salinity and pH on the expression of some selected traits in the male guppy (Poecilia reticulata)- a small freshwater live-bearing promiscuous fish species. The findings revealed that both salinity and pH had significant effects on courtship behaviors (e.g. sigmoid displays and gonopodial thrusts). The results also showed significant effects of salinity on body size (e.g. standard length and body area) and skin pigmentation (e.g. orange spot area). However, the study found that manipulations of these climate change parameters had no significant effect on other color spot numbers and areas. These findings elicit further information about the environmental condition-dependent expression of reproductive traits of fishes, which would help to take necessary strategies for breeding, conservation and management of many fish species in a changing aquatic environment.