Language attrition, a subfield of Linguistics, has not received significant scholarly attention in Nigeria, especially when compared to other areas of bilingualism and second language acquisition. While limited research has been conducted, these studies have predominantly focused on the erosion of lexical items, neglecting other critical language domains such as orthography, morphology, syntax, semantics, and pragmatics. This paper aims to address this gap by investigating the level of orthographic attrition among Yoruba L1 speakers who regularly use English as a second language. The study employs a cross-sectional experimental method for data collection. Loss of orthography competencies were evaluated using Sentence Repetition Tasks (SRTs) in Yoruba, which contained two phrases (Bí ó tilè jé̩ pé and Kò ní í wá) that belonged to the rule of word division in orthography. They were used to test the respondents’ adherence to spelling conventions to 1974 standard orthography. Quantitative analysis technique like independent t-test was used to identify difference in the level of attrition between linguistics and non-linguistics students. The findings show that Eng_L1 & Eng_L2_1_6 both show trend-level significance with p = 0.077 and 0.089, respectively. Also, Yor_L1 (Yoruba as L1) shows trend-level significance (p = 0.079). Similarly, Eng_Frds_Schools was significance (p = 0.041). Among the experimented students who spelt the two phrases correctly and wrongly. In the same vein, Eng_Sibs_Parents was not significant, though p = 0.104 is approaching significance. However, in the second t-test row, p = 0.004 indicates a highly significant difference, confirming that orthographic performance is better in those who spell correctly. Also, for the Eng_Frds_Schools, results showed that statistically significant difference (p = 0.037 and 0.026) was observed, and this showed that students who spoke English with friends at school and spelled correctly had significantly lower attrition. The findings conclude that consistent use of English, particularly among peer-school mates for interactions, contributes significantly to orthographic retention, while early exposure L1 backgrounds also play important but more passive roles.