This mixed-methods study investigates the design and instructional practices of massive open online courses (MOOCs) instructors within the learning environment to address the cultural diversity and learner personalization needs. Leveraging a grounded theory approach, the researchers analyzed two rounds of email interviews (n1= 25; n2=19) with MOOC and open education leaders about cultural sensitivity and personalization in MOOCs. Those interviews led to the formation of a 30-item online questionnaire completed by 152 MOOC instructors. While many of the MOOC instructors within the sample did not fully grasp the complex issues of cultural diversity, most made attempts to modify their instructional practices to accommodate cultural variances. To address cultural and linguistic differences, instructors added subtitles to video content and offered transcripts for video or audio content. Additionally, instructors were careful with language use and hand gestures, used simplified language, slowed their pace of speech, made the course content easy to navigate, limited text by leveraging (multi)media, and encouraged learners to translate and localize content for their peers. Furthermore, many instructors favored collaborative, small group learning; however, instructors could not agree on best practices to establish these groups. Implications and future directions for MOOC instructors and instructional designers are offered.