Background Cigarette smoking is an important modifiable risk factor in kidney disease progression. Although long-term smoking has been associated with chronic kidney disease (CKD), its effect on kidney function in early stages has not been clarified. Objective To detect the early effects of smoking either active or passive on kidney functions. Methodology The current study was comparative cross sectional study conducted on 280 participants, 140 were non‑smokers and 140 were smokers (70 passive smokers and 70 active smokers). The two groups were comparable in terms of all parameters. We investigated the possible effects of smoking on kidney functions using both serum kidney function tests especially; serum urea, serum creatinine, serum cotinine levels and detection of albumin in urine. Smoking history, full Laboratory investigations, Ventilatory function test including (FEV1/FVC, FEV1, FEF 25–75%, VC and FVC) were done. Results Serum urea, serum creatinine, serum cotinine levels and urinary albumin were statistically significant higher in smokers group in comparison to nonsmokers, also the serum cotinine levels and urinary albumin were statistically significant in active smokers in comparison to passive smokers. There were positive correlations between the level of urinary albumin and pack/year (r = 0.9, p<0.05), smoking index (r = 0.9, p<0.05), smoking duration (r = 0.4, p<0.05), and serum cotinine (r = 0.6, p<0.050) with good statistical significance. The most significant predictive risk factors of microalbuminuria among smokers group in descending orders were active smoking, passive smoking, age and serum cotinine level. Conclusion Both active and passive smoking, especially among heavy smokers, is a significant risk factor for microalbuminuria. This finding increase the importance of early cessation of smoking in order to minimize early renal affection among healthy smokers that may not be discovered by routine renal function tests.