P4P pilots in Tanzania showed signs of enhancing accountability in the health system. Internal accountability improved as P4P led to timelier and more constructive supervision that focused on problem-solving. It also reduced stockouts and interruptions in service delivery. External accountability increased as health workers were found to be more respectful and responsive to patients. Community involvement in facility governance was also strengthened under P4P. While resource limitations hindered some outreach activities, P4P increased the number of outreach visits when measured at the district level. In conclusion, P4P demonstrated potential to improve various accountability mechanisms in the health system.