Net asset value (NAV) for the Jersey-based firm rose from £1.73bn to £1.81bn since March 2017, with a total income of £81m thanks to investments from the previous year.
Infrastructure managing partner Phil White said: “Our investments have delivered strong NAV growth and income to the company, through our focus on engaged asset management.”
With a £0.039 dividend to be distributed in January 2018, 3i Infrastructure has seen a total return of £121m.
The group warned of increased competition across infrastructure subsectors despite a lack of greenfield PPPs at procurement stage in the UK and France.
Earlier this year, 3i announced the first close of the 3i European Operational Projects Fund.
Meanwhile, the company appointed Robert Jennings as a non-executive director, following the resignation of Steven Wilderspin.