Porous breakwaters using a caisson-pile group can increase the resistance of the vertical coastal structures in harbors to external heavy impacts, and also help facilitate the exchange of water. This article presents experimental results for the hydraulic performance of independent caisson-pile type breakwaters having three rows of vertical piles, both evenly and unevenly spaced between rows. Compared with even spacing, uneven, sparser spacing tends to have lower wave reflections and higher energy loss coefficients. Wave transmission, by contrast, appears not to be considerably influenced by spacing pattern. The transmission coefficient increases with wave steepness (S_0,s) and decreases with the ratio of the (total) width of the three pile rows to the wavelength (W/L_0,s).