Efficiency measurement has received increased attention amid global changes and growing competition within the finance industry in all countries, including developing countries such as Yemen. The evaluation of efficiency is crucial for players in the industry, not only to assess their ability for survival, but also to remain competitive in the market. Besides, efficiency would have consequences on other areas including bank margins and earnings manipulations. Like others, Yemen's banking industry has witnessed structural changes over the past decade, which paved the way for the industry to upgrade its efforts to emulate international standards. The present study analyses the efficiency of Yemen's banking sector during the 1996-2011 period. A two-stage analysis using Data Envelopment Windows Analysis (DEWA) was employed in the first stage of the research to measure the efficiency trends of industry, followed by the panel regression technique in the second stage to examine the determinants of efficiency. As efficiency of is a major concern for all stakeholders given its implications for various areas of banking operation such as bank margins and the opportunistic behaviour via discretionary accruals "manipulation" of earnings, the study also examines on whether the effeciency would have impacted the bank margins and earnings quality.