The perishable nature of vegetables demands an effective and reliable chain/channel of distribution for fast disposal. Performance of the existing distributive channels, marketing efficiencies of the channel operators and factors that influenced the marketing efficiencies of the marketing operators are integral to effective marketing. Much attention has not been given to this in the agricultural marketing literature in Nigeria. Marketing efficiency analysis revealed that marketing of onions by bulk merchants, wholesalers and retailers is most efficient in one of the selected markets at 149%, 343% and 275% respectively. Transaction loss, sales volume, transportation cost, wages, association dues, stall rent and cost of capital are factors that affect onion marketers in the study area.