In developing countries, chicken trade is characterized by complex chains comprising of many actors with limited biosecurity. This increases the spread of chicken diseases like Newcastle disease (ND). In Kenya, there is lack of uniformity in practices used in live bird markets, leading to increased disease outbreaks. This study aimed at assessing the effects of the chicken marketing practices on the frequency of ND outbreaks. A Poisson regression (PRM) was used on data collected from 336 traders selected using multi-stage sampling in Kakamega, Machakos, and Nairobi. Results highlight the low access of trainings and credit by traders. From the PRM results, breed composition, market channel, transportation, origin of birds, mixing of birds, slaughter of birds, disposal of waste, and housing as well as trader attributes like ND awareness, licensing, gender, and age had significant effects on the frequency of ND outbreaks. The study recommends that County governments collaborate with development partners to develop innovative ways of disseminating information on ND. The County governments should invest in market infrastructure such as slaughter facilities, special shelters and waste disposal equipment. There is also need for enforcement of biosecurity and hygiene measures through regular market inspections.