WSP said that it expects to close the deal to acquire Indigo Planning Ltd at the end of April.
Indigo Planning has 90 staff operating out of offices in London, Manchester, Leeds, Birmingham and Dublin.
It is one of the largest independent town planning consultancies in the UK, providing planning advice on all kinds of developments, including residential and commercial.
Indigo Planning chief executive, Simon Neate said: “This move represents the next phase in Indigo Planning’s evolution and will create new and bigger opportunities for both our colleagues and our clients in the UK and internationally.”
WSP UK chief executive Mark Naysmith said: “Our newly combined skills will increase the strength and diversity of our service offer for our clients across the UK.”