Abstract Background Coccidioidomycosis (CM) is a common cause of community-acquired pneumonia where CM is endemic. Manifestations include self-limited pulmonary infection, chronic fibrocavitary pulmonary disease, and disseminated coccidioidomycosis. Most infections are identified by serological assays including enzyme-linked immunoassay (EIA), complement fixation, and immunodiffusion. These are time-consuming and take days to result, impeding early diagnosis. A new lateral flow assay (LFA; Sōna; IMMY, Norman, OK) improves time-to-result to 1 hour. Methods We prospectively enrolled 392 patients with suspected CM, compared the LFA with standard EIA and included procalcitonin evaluation. Results Compared with standard EIA, LFA demonstrates 31% sensitivity (95% confidence interval CI, 20–44%) and 92% specificity (95% CI, 88–95%). Acute pulmonary disease (74%) was the most common clinical syndrome. Hospitalized patients constituted 75% of subjects, and compared with outpatients, they more frequently had ≥3 previous healthcare facility visits (P = .05), received antibacterials (P < .01), and had >3 antibacterial courses (P < .01). Procalcitonin (PCT) was <0.25 ng/mL in 52 (83%) EIA-positive patients, suggesting infection was not bacterial. Conclusions When CM is a possible diagnosis, LFA identified nearly one-third of EIA-positive infections. Combined with PCT <0.25 ng/mL, LFA could reduce unnecessary antibacterial use by 77%. Coccidioidomycosis commonly causes community-acquired pneumonia in endemic southwest United States. It is routinely diagnosed by enzyme immunoassay, complement fixation, and immunodiffusion. A novel rapid lateral flow assay (Sōna; IMMY), when combined with procalcitonin, could reduce unnecessary antibacterial utilization by 77%.