Extensive research has confirmed CLIL linguistic benefits but the evaluation of its textbooks and practitioners' performance is still relatively scant. Thus, the aim of this study is to evaluate a customised language-oriented CLIL textbook and the teacher's teaching performance of using it. The textbook was produced by a research team and used for 18 weeks by English majors in a national polytechnic university of Taiwan. After the one-semester trial, two well-established questionnaire surveys were respectively administered to examine 55 learners' judgement of the quality of the textbook and their evaluation of the practitioner's teaching quality. The results indicated that the learners welcomed the idea of integrating language and content learning into a single course, but were also concerned about the quality of its design for facilitating critical thinking, assessment, meaningful learning, and technology inclusion. The learners' English levels and their preferable future jobs significantly affected their attitudes towards the CLIL course. However, they exhibited relatively high satisfaction and agreement with the CLIL practitioner's performance of facilitating exposure to input, meaning-focused processing, form-focused processing, opportunities for output production, and use of learning strategies. The study has implications for CLIL material development and evaluation, particularly in the under-researched context of higher education.