Today’s educational system tends to include students with disabilities in the regular system. Accordingly, teachers of today’s educational system are encountered with numerous challenges of inclusive practice that require the necessity for constant professional development, which refers to the planning and implementation of strategic support in teaching students with disabilities that will contribute to modern directions of inclusion, namely to developed educational system. Therefore, in order to implement successful and quality inclusion and create a unique educational system, teachers use various support strategies. The aim of this research is to determine the frequency of usage of support strategies of teachers in teaching students with disabilities in regular primary schools in the Republic of Croatia, respectively to compare whether the adjustment of learning content, adjustment of methods, means and forms of work, adjustment of requirements and encouragement of social relations as four categories of strategies differ according to their average frequency of application and to determine whether there are differences in the frequency of their usage between teachers of different length of service and between primary class teachers versus primary subject teachers. The research involved 155 class and subject teachers of regular primary schools who had experience in working with students with disabilities during their internship. For the purposes of this research, a questionnaire of support strategies was modified and divided into four categories according to the support plan of the authors Ivančić and Stančić (2006; according to Radetić-Paić, 2013). The results of the research showed that there is a statistically significant difference in the frequency of application of the above mentioned categories of support strategies, but it is relatively small. Teachers use all the above categories of support strategies often, only some more often than others. The results also showed that there is no statistically significant difference in the usage of categories of support strategies between teachers of different length of service, while a statistically significant difference between class and subject teachers was shown only in the category of adjustment of methods, means and forms of work. Conducting this research contributes to the development of quality inclusive education and insight into the true implementation of inclusion in practice.