The immediate response of animals to fluctuations in any managemental practices or environmental temperature is an alteration in their physiological responses. For those who failed to deal with, their production performance is affected to a great extent. In the present investigation, seasonal and periodical rhythmicity of economic traits and genetic parameters analysis for growth and first lactation traits of Sahiwal cows were performed. Analysis of variance revealed significant effect of period on all growth traits (P≤0.01) and first lactation traits under investigation. Effect of season of birth was significant (P≤0.05) on W6, W12, W18 and W24 whereas BW, W30 and WFC were not significantly affected. Furthermore, season effect was found to be non significant on different first lactation traits except FCI (P≤0.05). The estimates of heritability for BW, W6, W12, W18, W24, W30, WFC, AFC, FL305DMY, FLL, FCI and FSP were 0.12 ± 0.28, 0.67 ± 0.34, 0.49 ± 0.33, 0.19 ± 0.29, 0.19 ± 0.30, 0.42 ± 0.32, 0.43 ± 0.22, 0.11 ± 0.09, 0.26 ± 0.11, 0.09 ± 0.02, 0.02 ± 0.05 and 0.03 ± 0.03 respectively. The genetic and phenotypic correlations amongst most of the growth and first lactation traits were higher in magnitude. Therefore these results indicated that genetic associations and effect of environmental variations could be effective for formulating selection criteria on the basis of early expressed economic traits in Sahiwal cattle.