The nine-time Senior major winner, and twice Masters champion, produced a masterclass on the south Wales links as the 144-man field were buffeted by wind and forced to contend with severe downpours throughout the day.
After bogeying the first hole, Langer recovered with birdies on the third, fifth, sixth and eighth holes to make the turn three under par. He then bogeyed 11 and 17, but finished with a birdie on the last.
Langer won the 2014 Senior Open Championship at Royal Porthcawl by a record 13 strokes, finishing 18 under par.
He leads by one shot from Argentina’s Mauricio Molina and England’s Carl Mason, who holds the all-time win record on the European Senior Tour with 25 victories.
Nine golfers share fourth place on level par, including eight-time European Tour No 1 and victorious 2010 Ryder Cup captain Colin Montgomerie.
Lindrick’s John King, playing in the event for the third time, shot a six-over-par 77, and said: “It was a really tough day. I played well, but let a few silly shots spoil a good round.”
Even so, he fared two shots better than six-time major winner Sir Nick Faldo and also comprehensively outscored his playing partners, with four-time European Tour title winner Jose Rivero shooting 84 and American Barry Conser.