Background In community-acquired pneumonia (CAP), the role of biomarkers to shorten duration of antibiotic treatment has not been firmly established. We assessed the effectiveness of active feedback of treatment algorithms based on procalcitonin (PCT) and C-reactive protein (CRP), compared to standard care, on the duration of antibiotic treatment in patients hospitalized with community-acquired pneumonia (CAP) in non-ICU wards. Methods and findings We performed a randomised, open label, parallel group, multi-centre trial in 3 Dutch teaching hospitals. Treatment was guided by a PCT algorithm, CRP algorithm or standard care. Participants were recruited by a member of the study team and randomised at day 2–3 of admission in a 1:1:1 ratio. Treatment was discontinued upon predefined thresholds of biomarkers that were assessed on admission, day 4 and days 5–7 if indicated. The primary outcome was total days on antibiotic treatment until day 30. In total 468 participants were included in this study. The median days on antibiotics (IQR) was 7 (IQR 7–10) in the control group, 4 (IQR 3–7) in the CRP group (rate ratio (RR) of 0.70, 95% CI 0.61–0.82 compared to standard care; p <0.001), and 5.5 (IQR 3–9) in the PCT group (RR of 0.78, 95% CI 0.68–0.89 compared to standard care; p <0.001). New antibiotics within the first 30 days were prescribed to 24, 23 and 35 patients in standard care, CRP and PCT groups, respectively. The hazard ratio for a new prescription in patients in the PCT group compared to standard care 1.63 (CI 0.97–2.75; p = 0.06). No difference in time to clinical stability or length of stay was found. Conclusions A strategy of feedback of CRP-guided and PCT-guided treatment algorithms reduced the number of days on antibiotic in the first 30 days after hospital admission in non-ICU wards for CAP. The study was not powered to determine safety of shortening duration of antibiotic treatment. (NCT01964495).