Emergency crews were called to the old Joseph E. Seagram & Sons bottling plant in the 7100 block of Sollers Point Road about 3:49 p.m. by the man's friend, who had also been on the catwalk but did not fall, said Capt. C. Ross Cooke, a fire spokesman.
The plant, closed in the late 1980s, has multiple buildings, some of which are gutted with unsecured stairwells, Cooke said.
It appeared the catwalk the men were on "gave way" as they were walking along it, Cooke said.
The man, who has not been identified, was taken to Maryland Shock Trauma Center in critical condition, Cooke said.
Cooke said he did not know why the men were in the plant, but police would likely be investigating the incident.