The purpose of this paper is to explore whether the use of attitudinal language stands as a potential source of effectiveness in undergraduate academic writing in English as a Foreign Language (EFL). In order to achieve this purpose, interpersonal features of a corpus of essays written by Mexican undergraduate students of English Language and Literature were analyzed. The model of appraisal (Martin, James R. & Peter R. R. White. 2005. The language of evaluation: Appraisal systems in English. Basingtoke: Palgrave Macmillan) was used to trace and contrast attitude resources of affect, judgement and appreciation in academic essays in relation to the grades they were granted by university professors at different levels of instruction. The results of the study confirm a significant relation between the use of resources of attitude and the perceived (in)effectiveness of the analyzed texts, as well as factors which potentially determine the nature of such relation and pose relevant implications for academic writing instruction in EFL in the context of the analyzed corpus.