Vectren shareholders will receive $72 in cash for each share held, representing a premium of nearly 10 percent to Vectren's Friday close.
The deal is the latest in a string of mergers in the U.S. power utility sector as consumption in many parts of the country flattens.
The deal will take CenterPoint's reach beyond Arkansas, Louisiana, Minnesota, Mississippi, Oklahoma and Texas to Vectren's core markets of Indiana and Ohio.
CenterPoint Energy will also assume all outstanding Vectren net debt, the companies said in a statement.
Reuters reported earlier on Sunday that both companies were nearing a deal.