An experimental study of natural convection heat transfer from heat staggered Pin fin array within air filled rectangular enclosure has been performed experimentally. It has been done to analyze the effects of several inducing parameters on system performance. The study has been done at wide ranges of influencing parameters such as Rayleigh number (328,042 ≤ Ra ≤ 794,323) and fin spacing (25 mm ≤ S ≤ 100 mm) and at a given fin height (L = 25 mm). The present study reported that the average Nusselt number (Nu) always increases by increasing Ra. While, by decreasing in fin spacing Nu increases initially up to an extreme value then tends to decrease. The fin effectiveness decreases continuously by increasing in Rayleigh number. It has been found that by decreasing in fin spacing, fin effectiveness increases initially up to a maximum value, beyond which it tends to decrease with further decrease in fin spacing. The correlations are developed for Nu as a function of dimensionless number (S/H) and Rayleigh numbers (Ra) and verified with experimental data.