Intonation is one of the most problematic aspects of the English prosody for L2 speakers. Studies on Nigerian English (NigE) intonation have claimed that Standard English intonation differs significantly from native Englishes but studies on the interpretation and production of accentual intonation tunes of L2 acquisition have been rare. Fifty final-year university undergraduates from Nigeria (25 males and 25 females) were purposively sampled. Each of the respondents was given 10 English sentences to produce and interpret. Interpretations of each of the respondents was captured and converted to simple percentages while the voice production of each of the respondents was elicited from a Speech Filing System (SFS) installed on Hp250 laptop. Respondents' frequency of occurrence at production level showed appropriate use of 134 (26.8%) while inappropriate use amounted to 366 (73.2%) out of 500 expected results of accentual tunes. Production on gender basis revealed males and females appropriate use at 67 (13.4%) each and inappropriate use was 183 (36.6%) respectively, both sexes showing no difference in accentual tunes use. Findings revealed that out of the 500 expected results for interpretation of accentual tunes, respondents appropriately interpreted the English sentences in 360 (72%) instances while 140 (28%) respondents misinterpreted the English sentences. Though, results of respondents revealed competence in the interpretation of accentual tunes (72%) but at the production level, respondents did not apply accentual tunes (26.8%) on English expressions. This study concludes that Nigerian spoken English accent differs significantly from native Englishes and should be described as an outer circle English.