Textbooks play a pivotal role in providing linguistic input and facilitating second language acquisition. This study aims to evaluate the pedagogical effectiveness of the "Al-Tariq ila al-Arabiyya" series, consisting of five parts (published by the Fanar Islamic Cultural Center - Qatar), in light of Stephen Krashen's theory, which includes hypotheses: acquisition versus learning, comprehensible input (i+1), natural order, monitoring, and the affective filter. The study adopted a mixed-method content analysis approach (quantitative and qualitative), analyzing a stratified random sample of 25 lessons (5 lessons from each part), resulting in 1959 codable semantic units. Quantitative results showed that the conscious learning hypothesis had the highest frequency (58.3%, 1143 cases), while the affective filter had the lowest (0.3%, 6 cases). The comprehensible input and natural order hypotheses together accounted for 39.7% of the cases. The goodness-of-fit test (chi-square) confirmed a significant imbalance in the distribution of hypotheses (χ²(4) = 2187.506, p < .001, V = 0.528), and the independence test indicated statistically significant differences between parts (χ²(16) = 321.245, p < .001, V = 0.202). Qualitative analysis using NVivo software revealed dominance of "linguistically structured inputs" patterns (86% of codes) alongside notable deficiencies in "affective motivations" and "self-monitoring." The series strongly aligns with three hypotheses (explicit learning, comprehensible inputs, natural order) and demonstrates high potential in teaching grammar and reading comprehension. However, limited attention to affective factors and monitoring may restrict learners' motivation and fluencyRecommendations include integrating interactive activities, language games, and self-assessment tasks to enhance alignment with Krashen's framework. This study fills a gap in the theoretical evaluation of Arabic teaching materials and provides a basis for development.