Uncertainties arising from market fluctuations limit choices of banana famers under contracts. However, they can opt not to renew their contracts with multi-national firms to sell to spot market or diversify. This paper examines optimal portfolio of Cavendish banana products of contract and non-contract farmers under uncertainty. We explore the effect of diversification by including banana flour from rejects aside from fresh banana. Constrained M-estimation of parameters and robust portfolio optimization results show that (1) non-contract farms benefit more from diversifying compared to contract farms; and (2) prices are higher for non-contract farms but profits are lower compared to contract farms.