The two premiers are expected to talk about European Union-related topics and Croatia's upcoming accession, the improvement of economic relations, and cooperation in infrastructure and tourism.
Bulgaria and Borisov strongly supported Croatia's EU accession, anticipating that it will stabilise the situation in the Balkans and strengthen the influence of smaller EU members.
Croatia and Bulgaria belong to the Friends of Cohesion, a group of EU countries receiving more than they pay into the EU budget and advocating that the cuts in the EU budget should not be to the detriment of the cohesion funds used to finance projects aimed at reducing the differences between rich and poor EU regions.
Bulgaria was the third EU country to ratify Croatia's EU accession treaty, doing so on 17 February 2012 with the assessment that Croatia had travelled a tough path since applying for membership and achieving "impressive progress" in the process.
Borisov visited Zagreb in April 2011, when a Croatian-Bulgarian economic forum was held.
This will be Milanovic's first visit to Bulgaria as prime minister.