The use of medicines and nurses’/midwives’ adherence to standard treatment guidelines (STGs) were examined in Timor-Leste during the early stage of the nation’s new health system development. A cross-sectional study was conducted as the quantitative element of mixed methods research. Retrospective samples from patient registration books and prospective observations were obtained in 20 randomly selected rural community health centers. The medicines use indicators, in particular the level of injection use, in Timor-Leste did not suggest overprescription. Prescribers with clinical nurse training prescribed significantly fewer antibiotics than those without such training (P < .01). The adjusted odds ratio of prescribing adherence for clinical nurse training, after accounting for confounders and prescriber clustering, was 6.6 (P < .01). STGs for nonphysician health professionals at the primary health care level have potential value in basic health care delivery, including appropriate use of medicines, in resource-limited communities when strategically developed and introduced.