The objective of this study was to evaluate five species of green manure as improved fallow on cassava yield. The trial design was a complete randomized block with three repetitions. The treatments consisted of different species of green manure and one control. Two cassava varieties Mayombe and Sawasawa were used. The yield was significantly enhanced by Tithonia diversifolia up to 343.02% for Mayombe variety compared to the control, ie 44.17 t/ha against 9.97 t/ha for the control. Also, the yield of Sawasawa variety, was high in the order of 390.4%, i.e. 38.4 t/ha against 7.83 t/ha for the control with no fertilizer. In addition, Lab lab species enhanced also the yield to 309.2% or 40.80 t/ha for the Mayombe variety against 9.97 t/ha for the control, as for Sawasawa variety, the yield was improved by 119.6% or 17.2 t/ha against 7.83 t/ha for the control. Other species, including Mucuna preta, Crotalaria grahamiana and Crotalaria ochroleuca, improved yield of the Mayombe variety in the order of 137.7%, 129.3% and 62.7%, respectively. For Sawasawa variety, only Crotalaria grahamiana improved its yield by 106.5% compared to the control.