Diarrhea can affect the health, performance, and welfare of preweaned dairy calves. The objectives for this project were to determine (1) associations between a positive test for a fecal pathogen and the probability of a calf showing clinical signs of diarrhea and (2) the impact of number of positive fecal tests on calf growth. The study population included dairy heifer calves (n = 54) on a commercial dairy that were enrolled in a 2 × 2 factorial study design examining a direct fed microbial and 2 milk programs. Feces were collected weekly for the first 4 weeks of life and tested for presence of 4 fecal pathogens: Rotavirus (ROT), Coronavirus (COR), E. coli K99 (F5) (ECO) and Cryptosporidium (CRP) (Enterichek). Clinical diarrhea was identified using a standardized fecal score that combined observations of odor, consistency, fluidity and color. Calves were weighed at birth (BW) and 5 weeks of age (WT5). The association between pathogen and diarrhea was evaluated with a logistic regression model (PROC GLIMMIX, SAS) with calf as a random effect and an autoregressive covariance structure. The association between weight at 5 weeks and number of positive fecal tests was evaluated using a linear regression model (Proc Mixed), controlling for initial weight and calf age. At 2 weeks of age calves were 5.8 times [95% CL: 2.2 to 15.3] as likely to test positive for at least one fecal pathogen compared with 4 (P < 0.001). Controlling for age, calves that tested positive for CRP were 2.8 times [95% CL: 1.2 to 6.4] as likely to show clinical signs of diarrhea (P < 0.05). Rotavirus and ECO were not associated with clinical signs of diarrhea. E. coli, CRP, and COR were not significantly associated with WT5. Rotavirus was associated with WT5 (P < 0.05). Calves with ROT at 1 or 2 time points weighed 5.1 ± 1.9 kg (LSM ± SEM) and 5.3 ± 1.9 kg (LSM ± SEM) less than calves that never tested positive, respectively (P < 0.001). In conclusion, although considered to be associated with a single diarrheal complex, specific pathogens may have different effects on growth, and knowledge of pathogens present may provide greater insight into treatment and management of calves with diarrhea.