There are a total of 52 achievements. These achievements can be viewed in steam under: Community -> View all [No. of games] games -> View Stats (Under Day of Defeat: Source)

Achievement	How to unlock
AWOL	Play on 5 non-official Day of Defeat Source maps
Beachhead	Capture the final flag to win a round
Black Maria	Get 250 kills with the K98k's Rifle Grenade
Bolt Action	Get 500 kills with the K98k
Broomhandler	Get 150 kills with the C96
Capo	Get 500 kills with the Thompson
Carbineer	Get 150 kills with the M1 Carbine
Carpet Bomber	Get 250 kills with the Garand's Rifle Grenade
Clean Sweep	Win Dod_Colmar without the other team detonating any bombs on your objectives
Combat Engineer	Defuse 100 enemy bombs
Cookin' With Gas	Get 500 kills with the Garand
Cutthroat	Get 150 kills with the Knife
Demolition Man	Plant 100 bombs on enemy objectives
Dig For Victory!	Get 150 kills with the Shovel
Dogface	Get 1000 kills as the Rifleman player class
Don't Bring a Gun	Win a knife fight
Don't Tread on Me	Block a Flag Capture that would have won the round for the enemy team
Double Cross	Kill an enemy by throwing back one of their team's grenades or riflegrenades
Egg Layer	Get 250 kills with the US Frag Grenade
Eviction Notice	Kill a deployed sniper or machinegunner from a distance greater than 100 feet with a rocket
Hail Mary	In Dod_Jagd, plant a bomb that explodes in overtime to extend the round
Head Hunter	Get 1000 kills as the Sniper player class
HEATer	Get 1000 kills as the Rocket player class
Iron Cross	Get 5000 kills as an Axis player
Jack of All Trades	In a single life, get a kill with an MG, Sniper Rifle, Rifle, SubMG and a Grenade
Johnnie Gun	Get 500 kills with the .30 Cal
Kilroy Was Here	Score 8 machinegun kills from a single deployed position
Knuckleduster	Get 150 kills with your fists
Linoleum Ripper	Get 500 kills with the MG42
Marksman	Score 5 consecutive headshots in a single round without dying
Medal of Honor	Get 5000 kills as an Allied player
Nuts!	Block 100 Flag Captures
Old School	Get 150 kills with the Colt
On the Warpath	Score 100 Flag Captures
Point Man	Get 1000 kills as the Assault player class
Potato Masher	Get 250 kills with the Stick Grenade
Putsch	Kill a machinegunner who has killed 8 or more players from a single deployed position
Rationing	Kill 4 or more players with a single grenade, riflegrenade or bazooka shot
Rocket Powered	Get 500 kills with the Bazooka
Roscoe	Get 150 kills with the P38
Sometimes the BAR	Gets You Get 500 kills with the BAR
Squaddie	Get 1000 kills as the Support player class
Storm of the Century	Get 500 kills with the MP44
Take No Prisoners	In a single life, kill 4 or more players in the victory time after winning a round
Tank Terror	Get 500 kills with the Pschreck
The Big Burp	Get 500 kills with the MP40
The Iron Curtain	Get 1000 kills as the Machinegunner player class
The Producer	Get 500 kills with the Springfield
Trophy Collector	Score 5 or more kills in a single life using scavenged enemy weapons
War Hero	Complete all Achievements
Warlord	Win 100 rounds
Wilhelm Tell	Get 500 kills with the K98 Sniper Rifle