This paper serves as a literature review of online learning as an innovative model of Teachers’ Professional Development (TPD) in the digital era. TPD is an important element for the quality of education because it affects teacher performance and student achievement. Therefore, TPD is designed to prepare teachers to perform their duties and profession well. Teachers in the 21st century encounter new challenges as a consequence of the Information and Communication Technology (ICT) integration in all areas. Online learning is developed using a Web 2.0-based digital technology. This is in order not only to improve the quality of education in the digital age but also to bring positive outcomes. This can be done by making information more easily accessible, helping to increase knowledge and skills easily, and providing an affordable training more available for teachers and overcomes the barrier of time, space, and cost at the same time. Several studies have been conducted to figure out the different results of TPD and its impact on students by comparing the traditional learning versus online learning, although more studies have been conducted on courses at the university level which have more diverse levels of studies and methods. In general, there was no significant difference on the teachers’ performance in the traditional learning versus online learning, but there was an increase in knowledge, performance and beliefs as well as interaction in the online and blended communities, which had an impact by increasing the TPD effectiveness.