Continuous education and updating knowledge and skills for nurses is very important, because they working in diË™erent shifts, do not have the opportunity to participate in face-to-face teach-ing sessions; self-educating methods are is very useful for them. Online, computer-based learning has emerged as an alternative means of providing continuing education to nurses. The aim of this study was to assess the eË™ect of online-learning module on nursesâ€™ knowledge and practice regard-ing Arterial Blood Gas (ABG) interpretation in critical care units. Design: A quasi-experimental design was utilized in the conduction of this study. Setting: the study was carried out in the respira-tory ICU and coronary care unit aÃ¿liated to Ain Shams University Hospitals. Sample: a purpo-sive sample of (60) staË™ nurses. Tools: data were collected through three tools; 1. Nursesâ€™ self- administered questionnaire; it included two parts: A. characteristics of the studied Nurses, B. Nursesâ€™ knowledge assessment tool to assess the level of nursesâ€™ knowledge regarding ABG inter-pretation. 2. Nursesâ€™ practice checklist to assess nursesâ€™ level of practice regarding ABG interpre-tation; both tools used pre and post implementa-tion of the online-learning module 3. Nursesâ€™ satisfaction questionnaire to assess the level of nursesâ€™ satisfaction regarding Arterial Blood Gas (ABG) interpretation post implementing online learning module. Results howed that there were a highly statistically signiï¬cant diË™erence of nursesâ€™ level of knowledge and nursesâ€™ level of practice before and after implementation of online-learning module (X2 = 53.333; 58.800) re-spectively at p. <0.001. The results also re-vealed that there was a positive correlation asso-ciation between nursesâ€™ total satisfactory level of knowledge and total satisfactory level of practice pre and post implementation of online-learning module (r = 0.566, 0.809) respectively. Conclu-sions: The level of nursesâ€™ knowledge and level of nursesâ€™ practice regarding Arterial Blood Gas (ABG) interpretation increased signiï¬cantly after implementing the online-learning module. Rec-ommendations: The study can be replicated on a large sample to generalize ï¬ndings. Incorporat-ing online-learning module related to ABG inter-pretation into the continuing professional devel-opment courses for critical care nurses is recom-mended.