The capital increase will allow shareholders that own 10 preferential subscription rights to subscribe for three new shares at 29.50 euros per share, Alstom said in a statement.
The company said it expects to close the acquisition of Bombardier's rail unit in the first quarter of next year.
French conglomerate Bouygues, which owns 9.7% of Alstom, has committed to participate in the rights issue, the company said in a statement.
Alstom in September lowered its offer for the business.
The two companies announced revised terms of an agreement which gives the rail unit an enterprise value of $8.4 billion, in a deal that would allow the cash-strapped Canadian firm to pay down some of its $9.3 billion in debt.
($1 = 0.8439 euros)
(Reporting by Matthieu Protard; editing by Louise Heavens and Jason Neely)