Study was performed to investigate the influence of different sources of condensed tannins (CT) supplementations on ruminal fermentation and rumen microbial diversity changes of goats. The objective of this study was to determine whether the tannin-containing sericea lespedeza leaf pellet (SL, Lespedeza cuneate; 13.6% CT), ground pine bark (PB; Pinus; 16.3% CT), or its combination (SL+PB) would have effects on rumen fermentation and microbial diversity in meat goats. Twenty-four Kiko-crossbreed intact male goats (Capra hircus; BW = 38.6 ± 2.7 kg) were randomly assigned to 4 treatments (n = 6): 1) 30% bermudagrass hay and 70% grain mix, 2) 30% PB and 70% grain mix, 3) 30% SLP and 70% grain mix, and 4) 15% PB, 15% SL pellet, and 70% grain mix. Each treatment diet (30% DM) was mixed with remainder of each diet (70% DM) contained 70% commercial sweet feed and 30% alfalfa pellets. Feed intake and BW were monitored every 2 wks for 42 d. Rumen fluid samples were taken using a stomach tube at the d 0, 20, and 42 for microbial DNA analysis. Overall, there were no differences in DMI and BW gain among treatments. However, goats supplemented with PB and SLP+PB diets decreased (P < 0.05) concentrations of acetate, isobutyrate, and isovalerate compared with those in the control and SLP diets. There were no differences in rumen microbial kingdom (fungi, bacteria, and archaea) and phylum diversity. However, green algae population in rumen fluid was greater (P < 0.01) for control diet than for other treatments. In this study, Bacteroides (30 to 55%) and Firmicutes (30 to 47%) were the major bacterial phylum, while Prevotella spp. was the most predominant rumen bacterial species in the percentage of 22.1, 42.2, 28.9, and 23.9 for control, PB, SLP, and mixed diets, respectively. The population of rumen bacterial species in PB-supplemented group was greater for Bacteroides spp. (P < 0.02), Marinifilum spp. (P < 0.04), and Oribacterium spp. (P < 0.03) compared with other treatment groups. However, population of Fibrobacter succinogenes was greater (P < 0.05) for SLP than for other treatments. Supplementing tannins in goat diets such as PB and SLP diets has a potential to modify rumen bacterial population.