It was the 30-year-old double Olympic champion's 11th individual (two-man or four-man) world title and 13th overall including two mixed-team triumphs.
The triumph caps an incredible season for Friedrich, one of bobsleigh's greatest of all time: across all his runs in both two-man and four-man events this season, he has only been beaten once, winning 39 of his 40 heats.
Runs of 53.22 seconds and 53.76 seconds on the last day of competition in Altenberg ensured a comfortable victory for Friedrich's quartet, who finished 0.79 seconds ahead of Austria's Team Benjamin Maier.
Bronze went to last year's silver medallists, Team Johannes Lochner of Germany.
Humphries makes history as first monobob champion
Earlier, USA's Kaillie Humphries made history as the first women's monobob world champion.
The two-time Olympic and four-time world champion in the two-woman discipline became the single-racer event's first winner after putting together strong third and fourth runs to overhaul day one leader Stephanie Schneider of Germany.
Humphries' third and fourth runs were both track records, with her 59.47-second last run standing as the new mark.
She outpaced Schneider by 0.50 seconds, while another home racer, Laura Nolte, took bronze.
The women's monobob will be on the Olympic programme next year at Beijing 2022.