Inter suffered a setback in their pre-season preparations as CSKA Sofia claimed a 2-1 victory thanks to goals from Arsenio and Preslav Yordanov.
Roberto Mancini's starting XI for a second friendly at their Riscone di Brunico training base featured plenty of experienced named, but it was the Bulgarian side who drew first blood when Portuguese winger Arsenio clipped a measured finish on the angle across Samir Handanovic and into the far corner.
Rodrigo Palacio engineered space in the area to smuggle home an equalizer in the 15th minute before Arsenio pounced on an error from Dodo but spurned a one-on-one opportunity to double his and his team's tally.
There was an even more glaring miss from Inter in the 31st minute when youngster Andrea Pinamonti won a penalty but saw his attempt from 12 yards pushed to safety by Bulgaria Under-21 international Georgi Kitanov.
Mancini changed his entire XI for the second period but a bolstered frontline of Mauro Icardi and Stevan Jovetic could find no answer to a 50th-minute winner.
Yordanov capitalized on some woeful defending to collect Arsenio's pass and slip a shot underneath replacement goalkeeper Juan Pablo Carrizo.