A total of 108 barrows weaned at 21 d (5.82 ± 0.96 kg initial BW) were used to determine the effects of dietary CP and dried citrus pulp (DCP; rapidly fermentable carbohydrate source) contents on VFA and ammonia concentrations in the cecal digesta of weanling pigs. Pigs were blocked by initial BW and randomly assigned to 1 of 4 treatments with 9 replicate pens per treatment and 3 pigs per pen in a randomized complete block design. Treatments were arranged in a 2 × 2 factorial, with 2 CP contents (HCP and LCP; high- and low-CP diets, respectively) and 2 DCP contents (0 and 7.5%, as-fed basis). The HCP treatments consisted of feeding 20 and 21% CP diets (as-fed basis) throughout the pre-starter I (1 to 14 d) and pre-starter II (15 to 28 d) phases, respectively. For the LCP treatments, CP contents were 16 and 17% for the pre-starter I and II diets, respectively. Crystalline AA were added to the HCP and LCP diets to maintain an ideal AA pattern. Cecal digesta samples were collected from 1 pig per pen on d 7 and 28 postweaning for determinations of VFA profile by gas chromatography and ammonia concentration by colorimetry. Data were analyzed as repeated measures using the MIXED procedure of SAS, with pen and block as the random effects and CP, DCP, day, and 2-way and 3-way interactions as the fixed effects. Pigs fed diets containing 7.5% DCP tended (P = 0.06) to have increased acetate concentration and decreased (P < 0.01) propionate, isovalerate, and valerate concentrations in the cecum. Cecal butyrate, isobutyrate, and total VFA concentrations were not affected by the treatments. There was a DCP × day interaction (P < 0.05) for isovalerate concentration, in which dietary inclusion of 7.5% DCP decreased (P < 0.01) isovalerate concentration only at 28 d postweaning. There was a CP × DCP interaction for ammonia concentration (P < 0.01), in which adding 7.5% DCP to the diet tended (P = 0.06) to decrease cecal ammonia concentration only for pigs fed the LCP diet. In conclusion, low-protein AA-supplemented diets with 7.5% DCP inclusion may reduce proteolytic fermentation in the cecum of weanling pigs.