There is a railway service available, which operates in the municipality. The 2 international railroads here are Sofia-Thessaloniki (through the border railway station Kulata) and  General Todorov- Petrich( a minor railroad).
At present people still don’t use the railway transport enough. For example, the international transport of passenger to Thessaloniki was stopped for a few years.
There are several trains a day in both directions Sofia- Petrich. For more information, please check the schedule of Bulgarian State Railways:
http://razpisanie.bdz.bg/site/search.jsp

There are a couple of buses a day from Sofia to Petrcih. For more information, please check the schedule of Central Bus Station-Sofia: http://www.centralnaavtogara.bg  or call the bus station in Petrich: 
tel. number: 0745/62136

There is a bus service which operates in all the villages in the region. The buses from Sofia to Petrich and vice-versa leave every hour from the central bus station in the Petrich.

Unfortunately, the international railway service for passengers to Thessaloniki was stopped for a few years, but now it’s already available.
There are 2 international bus lines which pass through the Petrich Municipality: Sofia-Strumitsa and Sofia-Thessaloniki.
There is only one bus a day, which travels from Sofia to Strumitsa and vice versa with a stop in Petrich.
There are only a few buses a day from Sofia to Thessaloniki and vice versa, as only one of the bus companies has a stop in Petrich.
For more information about the two  bus lines, please check the schedule of the Central Bus Station- Sofia: http://www.centralnaavtogara.bg