Rainfall variability in space and time is the characterics of arid and semiarid zones. Determination of factors influencing on rainfall of these regions such as Iran is important for forecasting purposes and water resource management. Ocean-atmospheric oscillations such as ENSO (El Ni?o Southern Oscillation) phenomenon have been known as one of the most important factors influencing on rainfall of specific areas. This study aimed to investigate the correlations between ocean-atmospheric oscillations and Iran rainfall. The correlations were investigated both monthly and seasonal. Monthly rainfall data from 50 synoptic stations with at least 30 years of records, up to the end of 2007 were used. (a) First, concurrent and lag relationships (0-3 lead-time) between ENSO and Iran monthly and seasonal rainfall were evaluated based on Southern Oscillation Index (SOI) and Indian and Pacific Sea Surface Temperature (SST) in Rainman software. Monthly and Seasonal time series were divided to several groups by four methods (Avarage SOI, SOI Phases, Indian SST Phases and Pacific SST Phases). Significant differences between rainfall groups in each methods were assessed by the non-parametric Kruskal-Wallis and Kolmogorov-Smirnov tests. The significant relationships for rainfall forecasting was validated by Linear Error in Probability Space (LEPS) test. (b) Then, Pearson correlation coefficients between Iran monthly and seasonal rainfall with North Atlantic Oscillation (NAO), North Caspian Pattern (NCP), Mediterranean Oscillation-Algiers/Cairo (MOac), Mediterranean Oscillation-Gibraltar/Israel (MOgi), Western Mediterranean Oscillation (WeMO), Mediterranean Circulation Index (MCI), Mediterranean SST (MSST) and Persian Gulf SST (PGSST) were analyzed. (c) Finally, for each season, the effective ocean-atmospheric oscillation indices in homogenous rainfall regions were identified by stepwise multivariate regression analysis. The results showed that, status of ENSO during summer (July-September) was related to autumn (October-December) and October rainfall in the west and northwest of Iran and the west Caspian Sea coast. The El Ni?o (Negative) phase is associated with increased rainfall and the La Ni?a (Positive) phase is associated with decreased rainfall. Using average SOI is useful index for rainfall forecasting in mentioned areas. According to results, Indian and Pacific SST phases are not suggested for rainfall forecasting in Iran. There is a significant correlation between NAO and monthly rainfall in northern and western parts of Iran. Also, a lag significant correlation between NAO and winter (January-March) rainfall in north-western and autumn rainfall in central and southern of Iran were identified. NCP has a simultaneous and positive correlation with monthly and seasonal rainfall over north of Iran. There was a weak Keyword: Rainfall, Ocean-atmospheric oscillations, ENSO, Rainman, Iran