The Tokyo-based communications giant posted a gross profit of Yen251,720 billion (pounds l.05 billion) for the period.
It claimed its performance was down to aggressive sales efforts and business initiatives, rather than a marginal improvement in the Japanese economy, which was not translating into greater consumer consumption.
Last summer, Japanese consumer confidence was at its lowest level since December 2005, because of a combination of rising fuel costs and falling share prices. However, economists say wages and employment are remaining solid.
A Dentsu spokesman said: "Although the Japanese economy sustained its mild recovery against a backdrop of improvement in corporate profits, which arose from strong imports and increased capital expenditures in the manufacturing industry, individual consumption did not show a full recovery and continues to fluctuate."
As a result, Dentsu focused on what it called "effective and efficient one-stop" solutions for clients last year.
It cited the positive impact of last summer's World Cup, the Asian Games in Doha and the FUVB Volleyball World Championships in Japan as factors in its improved sales.
Dentsu dominates the Japanese market, where it controls more than 40 per cent of all mass-media advertising, and has more than 6,000 clients.