This study examined the influence of demographic variables on adult language learners' English proficiency development. Specifically, it tried to ascertain the level of English proficiency of the respondents when grouped according to demographic variables such as gender, age, civil status, length of work experience, highest educational attainment, specialization, and designation. It also tried to find out if there are significant differences in the respondents' level of proficiency in the four macro-linguistic skills and if there are significant correlations between the respondents' English proficiency and the identified demographic variables. Using descriptive-correlational research design with academic professionals working in a higher education institution in the Philippines as respondents, this study found that the respondents have intermediate level of English proficiency (B1, CEFR), lower than what is expected from academicians in a higher learning institution. Findings further reveal that there are significant differences in the respondents' level of proficiency in the identified macrolinguistic skills and that age, educational attainment, and length of service are positively correlated with English proficiency, while gender, civil status, specialization, and designation are negatively correlated with the same. Implications of the findings are discussed in relation to curriculum development, language teaching and assessment, and language policy and planning.