Abstract: An experimental study on joint infection with Trypanosoma congolense (Tc) and Haemonchus contortus (Hc) was conducted in 30 female Yankassa sheep aged between 12 and 25 months, divided into 5 groups of 6 animals (TcHc, HcTc, Hc, Tc and control). Two groups received a single infection with either H. contortus or T. congolense and two other groups were infected with T. congolense followed by H. contortus (TcHc) in one and H. contortus followed by T. congolense (HcTc) in the other. One group was kept as uninfected control. All the trypanosome-infected groups (Tc, TcHc, HcTc) showed different prepatent periods, the Tc group was patent at day 10 post-infection (pi), while TcHc and HcTc were patent at day 5 and 7 pi, respectively. High mean parasiteamia was observed during the acute phase of the infection in the trypanosome infected groups, which declined during the chronic phase giving mean parasitaemic scores of 3.2±0.1 and 0.3±0.1. There was a rapid fall in the Packed Cell Volume (PCV) of the TcHc group, which reaches a minimum decline at day 25 pi. It was also observed that higher faecal egg count corresponded to decrease in PCV. All the Haemonchus infected groups developed higher eosinophils values, which was indicative of the activities of tissue invading helminthes.