The incident happened at around 5.20pm on Saturday in Pathhead, Midlothian.
The group of three men, aged 50, 53, and 54, were attacked by around four men who arrived in the street in two or three cars, including a red Peugeot and a blue Vauxhall Astra.
The victims suffered a variety of injuries, the most serious being a broken nose and cheek sustained by the 50-year-old man. All three received treatment at the Edinburgh Royal Infirmary.
A Lothian and Borders Police spokesman said: “We are appealing to anyone who was in Pathhead or the surrounding area around the time of the incident, who either saw the assault take place, or who saw the vehicles used by the suspects, to contact police immediately.
“Anyone else who has any other information that can assist out inquiries should also get in touch.”
Anyone with any information should contact Lothian and Borders Police on 0131 311 3131, or Crimestoppers in confidence and complete anonymity on 0800 555 111.