Inoculation of cattle with Propionibacterium acidipropionici strain P169, a commensal rumen bacterium known for its lactate and glucose utilizing properties, has been reported to modify the profile of ruminal VFAs in favor of increased propionate production. The objective of this study was to document shifts in rumen microbiota as a result of rumen inoculation with P169. Eight ruminally cannulated steers (434 ± 33 kg) were either not inoculated (control) or inoculated with P169 (1 × 10¹¹ cfu/head/day) by including it in the diet for 101 d. Rumen samples from liquid and solid fractions were collected every 3 wks. Genomic DNA was extracted and subjected to qPCR for quantification of P169 and Illumina sequencing of the V4 region of the 16S rRNA gene for community profiling. On average, 36,250 high quality sequences were generated per sample, resulting in identification of 16 and 15 bacterial phyla in liquid and solid fractions, respectively. No significant difference was detected in α-diversity indices between treatments. While PERMANOVA analysis of the UniFrac distances of microbial communities revealed distinct clustering of rumen liquid from solids (P = 0.03), β-diversity did not differ between treatments. Quantitative PCR identified a trend for an increase (P = 0.06) in the abundance of P169 in inoculated steers. Partial Least square discriminant analysis of sequence data found that the proportion of members of the Firmicutes (Clostridiaceae, Lachnospiraceae, and Ruminococcaceae, and Phascolarctobacterium), Bacteroidetes (Bacteroideales, families RFP12 and BS11), and Synergistetes (Pyramids) were increased (P < 0.05) in response to P169 (R² = 0.86, Q² = 0.57). Data suggest that while inoculation with P169 altered the proportions of bacteria within the rumen, it did not change the α or β diversities of bacteria in either liquid or solid bacterial communities.