BG said pre-tax profits for the full year were $2.97bn (Â£2bn), compared with a loss of $2.3bn in 2014.
On a quarterly basis, BG's losses improved from $8.3bn in the final quarter of 2014 to a loss of $1.17bn for the same period in 2015.
BG's results have been affected by the falling oil price.
BG Group's chief executive, Helge Lund, said: "We are pleased to have delivered an excellent operational performance in 2015 with results in line with, or ahead of, our guidance for the year.
"This strong operational performance is the result of the capability and commitment of our teams across the organisation and we will deliver a high-performing business into the combination with Shell."
BG's results come in the same week as those from other energy giants, BP and Shell.
Both maintained their dividend payout to shareholders. BG said its shareholders would receive Shell's 2015 fourth-quarter dividend and would not receive a further BG Group dividend for 2015.
Shell's fourth-quarter dividend is 47 cents per Shell share, which is equivalent to 20.93 cents per BG Group share.
Oil and gas firm BG Group, whose takeover by Royal Dutch Shell is almost complete, has reported a rise in its final full-year earnings.