Widjaja is a founding partner of Mahanusa. Within Mahanusa's asset management business, he together with his team initiated the company’s fixed income mutual fund products. Within Mahanusa's investment banking division, he has executed numerous transactions involving corporate and debt restructurings, fund raising, acquisitions and origination of fixed income products.

For nine years until 1998, Widjaja served as a Managing Director at Bank Kesawan. The bank was a joint venture with the state-owned Bank Ekspor Impor Indonesia Pension Fund. During his tenure with the bank, Widjaja expanded the banking operation from a single branch to 21 branches in seven major cities. He also upgraded the bank’s status to a Foreign Exchange Bank. At the time of his departure, Bank Kesawan was a Category A bank, the highest category according to Bank Indonesia’s bank evaluation benchmarks

Besides serving as co-chair of the Investment Committee, Widjaja also originated and executed most of Mahanusa’s direct investment transactions. He is also responsible for the administrative, legal and personnel issues concerning the investee companies. Widjaja sits on the Boards of all of Mahanusa’s investee companies, actively managing those entities.

Widjaja graduated from the Iowa State University with a BBA degree in Management Information Systems. He is a BAPEPAM licensed Broker-Dealer, Underwriter and Investment Manager Representative.