The asset pricing models have become important bottleneck for academic and portfolio managers. The question of whether the Fama-French five-factor model explains stock returns has been extensively investigated across the entire globe. This work is an endeavour to empirically investigate the GDP-Growth as mediating variable between various factors and portfolio returns using a broad sample of 522 financial and non-financial firms enlisted on Pakistan Stock Exchange between January-1993 and June-2022. The study employs the Structural Equation modeling and Ordinary Least Square regression to determine the findings before and during the Covid-19 epidemiological situation which has not received due attention by researchers. The analysis reveals that market and investment factors are redundant, whereas size and value show significant results, whereas GDP-Growth performs significant mediating impact for the whole time frame. Using before Covid-19 period, the results reveal that market, value, and investment are redundant, but size, profitability, and GDP-Growth are significant. During the Covid-19, the statistics indicate that market and investment are redundant, though size and GDP-Growth are highly significant, but value and profitability are moderately significant. The OLS regression shows that market and investment are statistically insignificant, whereas size is highly significant but value and profitability are marginally significant. Using the GDP-Growth augmented model, a slight growth in R-square is observed. The size, value and profitability factors are recommended to the investors for PSX.