The purpose of this study is to examine English new-language teachers' perceptions of online asynchronous and online synchronous professional development and teacher efficacy. English new-language students score significantly lower than others on standardized tests. This study analyzes online professional development for English new-language teachers to enhance teacher efficacy and thus bridge the achievement gap. This multiple-case study included four participants between the ages of 25 and 40. All participants are teachers certified to teach English to speakers of other languages, have a year or more of teaching experience, and are bilingual. The research methodologies used to inform this study include interviews, observations, professional development, and artifacts as main data sources. The participants went through two rounds of interviews and were observed in the classroom. The teachers were observed during professional development and the researcher collected artifacts from professional development for analysis. The researcher triangulated the data from these main data sources to identify codes, which were then developed into themes. The codes and themes were used to answer the research questions. The results of this study can make online professional development for English new-language teachers more efficient and help increase teacher efficacy. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]