The €15 million raked in by the midfielder's move to Manchester United will be largely spent on stadium and training base renovations, as well as a club merchandise store
The 23-year-old Japan international agreed a move to Manchester United in a deal reported to be worth an initial €15m, which could rise to €21m based on appearances and success.
Watze said the majority of that money will be spent on renovating the stadium and building a new training ground to nurture young talent, along with a new megastore to sell club merchandise.
"We will use the Kagawa money to cement our club's foundations," he told Bild. "Overall, we will invest about €12m on our infrastructure."
Plans include new VIP boxes in the Signal Iduna Park, renovation to the south stand of the stadium, a €3m youth training ground and a club megastore.
Kagawa was a bargain buy for Dortmund when he arrived from J-League side Cerezo Osaka for just €350,000 in 2010.