The study analyzed empirically the dynamics of rubber and cocoa exports from Nigeria within 1961 – 2010. It specifically estimated the determinants of their export performance and determined the degree of export diversification of the agricultural sector. Both export crops were chosen because they remained the most exported agricultural commodities after the number of agricultural exports commodities shrank from the traditional 12–15 commodities of the 1960s. Published national aggregates on specific trade and macroeconomic variables from reputable secondary sources were used. In the course of data analysis, descriptive statistics, diversification index and Error Correction Model (ECM) were employed. Prior to estimation, Unit root and Cointegration tests were conducted. The results revealed that export supply of cocoa was found to be influenced by export cost and rainfall in the long run while output, cost of production and export affected it in the short run. Rubber export supply was influenced by cost of export and exchange rate in the long run while world export-output ratio and cost of export affected it in the short run. The study results further revealed that export diversification measure showed that the sector experienced fluctuations with varying Hirschman indices which ranged from 1.3 x 10-7 to 5.1 x 10-7, depicting decreasing concentration. Invariably, this implies increasing leanness of the export basket. On the basis of the result, it is necessary to explore policy options such as export financing and foreign exchange policies to promote production in the export subsector of agriculture and industrial sector to diversify the national export basket.