Research Article Validity of Adult Psychopathology Model Using Psychiatric Patient Sample from a Developing Country: Confirmatory Factor Analysis Naser Abdulhafeeth Alareqe , 1 Siti Aishah Hassan , 2,3 Engku Mardiah Engku Kamarudin , 2 Musheer A. Aljaberi , 4,5,6 Mohamad Sahari Nordin , 7 Nadeem Mohamed Ashureay , 1 and Lubna Ali Mohammed 8 1 Department of Educational Psychology and Counseling, Taiz University, Taiz 6803, Yemen 2 Department of Counselor Education and Counseling Psychology, Faculty of Educational Studies, Universiti Putra Malaysia, UPM Serdang 43400, Malaysia 3 International Institute of Muslim Mental Health and Family Therapy (IMHAFT), Oxfordshire OX266YH, UK 4 Department of Community Health, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia (UPM), UPM Serdang 43400, Malaysia 5 Faculty of Medicine and Health Sciences, Taiz University, Taiz 6803, Yemen 6 Faculty of Nursing and Applied Sciences, Lincoln University College, Petaling Jaya 47301, Malaysia 7 Department of Educational Psychology and Counseling, International Islamic University Malaysia (IIUM), Kuala Lumpur 53000, Malaysia 8 Department of TESL, Lincoln University College, Petaling Jaya 47400, Malaysia Correspondence should be addressed to Siti Aishah Hassan; siti_aishahh@upm.edu.my Received 24 August 2022; Revised 29 November 2022; Accepted 30 November 2022; Published 21 December 2022 Academic Editor: S M Yasir Arafat Copyright © 2022 Naser Abdulhafeeth Alareqe et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Objectives. This study is aimed at testing and validating the two-factor measurement model of the Millon Clinical Multiaxial Inventory (MCMI). Specifically, this paper reported construct validity, particularly focusing on convergent and discriminant validities of the internalizing-externalizing MCMI model of adult psychopathology using a psychiatric sample from a developing country, the Republic of Yemen. Methods. MCMI was distributed among 232 outpatients from the Hospital of Taiz City and two private psychiatry clinics in Yemen; data were collected using structured interviews over four months. We used exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) to explore and confirm the latent structure MCMI and verify the evidence of convergent and discriminant validity. Results. The CFA results indicated that MCMI was a good fit for the internalizing-externalizing two-factor model of adult psychopathology, comparative fit index ðCFIÞ =0:95, and RMSEA = 0:07. The results of the CFA provide evidence of convergent and discriminant validity characterized by MCMI with the internalizing-externalizing model. Conclusion. The adult psychopathology of internalizing- externalizing is a valid measurement model of MCMI with ten personality disorders and eight clinical syndromes. 1. Introduction Children’s behavioral issues are now conceptualized differ- ently by researchers, clinicians, and educators as a result of Achenbach’s original findings on childhood psychopathol- ogy assessment [1, 2]. One of the fundamental aspects of the analyses is the hierarchical conceptualization of mental disorders in terms of two broad behavioral spectra, which Hindawi Mental Illness Volume 2022, Article ID 9594914, 12 pages https://doi.org/10.1155/2022/9594914