Play as Boris Becker - Successfully complete Singles in Arcade mode to unlock Boris Becker.

Play as Duke - Reach the number one rank in Professional mode to get invited to the King Of Players tournament. Win the tournament to play against Duke. Defeat Duke to unlock him.

Play as King - Reach the number one rank in Professional mode to get invited to the King Of Players tournament. Win the tournament twice to play against King. Defeat King to unlock him.

Play as Stefan Edberg - Successfully complete Doubles in Arcade mode to unlock Stefan Edberg.

Play as Tim Henman - Successfully complete all Tennis Academy Challenges on both the Beginner and Advanced difficulty to unlock Tim Henman.

World Tour training games - Successfully complete the indicated task to unlock the corresponding training game:

Alien Attack: Successfully complete Meat Defender Level 4.
Avalanche: Successfully complete Zoo Feeder Level 4.
Count Mania: Successfully complete Avalanche Level 4.
Court Curling: Successfully complete Pot Shot Level 4.
Drum Topple: Successfully complete Alien Attack Level 4.
Meat Defender: Successfully complete Pirate Wars Level 4.
Pin Crusher: Successfully complete Court Curling Level 4.
Pot Shot: Successfully complete Block Buster Level 4.
Zoo Feeder: Successfully complete Shopping Dash Level 4.

Fancy costumes - Successfully complete all levels of the indicated mini-game in World Tour mode to unlock the corresponding costumes for purchase. They must be worn in order to enter the Fancy Dress-only tournament.

Action Hero costume: Drum Topple (using a male player)
Bowling costume: Pin Crusher
Karate costume: Avalanche
Mariachi costume: Blockbuster
Mime costume: Count Mania (using a male player)
Pajamas costume: Court Curling
Pirate costume: Pirate Wars
Sheriff costume: Pot Shot
Skeleton costume: Meat Defender
Superhero costume: Shopping Dash
Zookeeper costume: Zoo Feeder

Accomplish the indicated achievement to get the corresponding number of Gamerscore points:

Fore! (10 points): Hit a line judge.
One Small Step... (10 points): Win your first match in the World Tour.
...One Giant Leap! (15 points): Win your first tournament in the World Tour.
Make Friends & Influence People (15 points): Make friends with 8 characters in World Tour.
Quick and Easy (15 points): Play and complete 25 events in Play mode.
Loving It (15 points): Achieve 25 Love Games.
Breaking the Speed Limit (15 points): Hit a serve over 200kph/124.28miles.
Big Hitter (15 points): Achieve 250 MAX Serves.
Pushing it to the MAX! (15 points): Achieve 3 Consecutive MAX Serves in a match.
Different Strokes (15 points): Win 400 stroke points.
Volleyball (15 points): Win 300 volley points .
Super, Smashing, Great! (15 points): Win 200 smash points.
Aces High (15 points): Score 100 Aces.
Over the Top (15 points): Win 50 lob shot points.
Drop and give me 50! (15 points): Win 50 drop shot points.
Your Country Needs You! (15 points): Be selected for the Davis Cup team or Fed cup in world tour..
Practise Makes Perfect (15 points): Win 10 Practice Matches in world tour.
Training to win (20 points): Clear a level 8 training game in the World Tour.
Schools Out (20 points): Clear each academy mission in the World Tour.
Shopaholic (20 points): Purchase 100 different items from the shop in world tour.
Versatile Male (20 points): Win a match with all Male Pro Players on default settings.
Versatile Female (20 points): Win a match with all Female Pro Players on default settings.
Marathon Man (20 points): Run a total of 10km.
Grass Stains (20 points): Play 100 matches on a Grass Court.
Play with Clay (20 points): Play 100 matches on a Clay Court.
Astro Carpet King (20 points): Play 100 matches on an Artificial Court.
King for a Day (25 points): Unlock the secret player King.
That Dukes a hazard! (25 points): Unlock secret player Duke.
Gold Medallist (25 points): Unlock every gold medal in the game..
Access all Areas (25 points): Purchase every Court Pass in World Tour.
Style Guru (25 points): Unlock every basic play style in World Tour.
Go Pro! (30 points): Turn professional in World Tour.
Leader of the Pack (30 points): Number 1 Amateur in the world.
National Treasure (30 points): Win the Davis or Fed Cup in World Tour.
First Amongst Equals (40 points): Rank #1 in the world in World Tour.
You are Gold! (30 points): Complete every academy mission with a gold medal in World Tour.
Last Man Standing (20 points): Beat all default Male Pro Players.
Last Woman Standing (20 points): Beat all Female Pro Players.
Competitive Streak (20 points): Complete 10 ranked matches in world tour.
Social Animal (20 points): Complete 10 player matches.

Additionally, there are ten secret achievements:

To be this good takes AGES (10 points): Score an Ace with an Underhand Serve.
Dr Doolittle (20 points): Feed all types of animal in a single game of Zoo Feeder.
Cherry Picker (20 points): Collect 10 cherries in a single game of Avalanche.
Block and Roll (20 points): Clear a 15 block combo in Blockbuster.
Arrrrrrr! (20 points): Sink 3 galleons in a single game of Pirate Wars.
Ham and Eggs (20 points): Bowl a Turkey on level 6 or above of Pin Crusher.
Perfect Frame (20 points): Clear the table of balls in order without missing in pot shot.
To Look this good takes SEGA (20 points): Play a game in the complete SEGA outfit.
Them Bones (30 points): Play the Meat Defender training game wearing the full Skeleton costume.
Secret achievement (30 points): Unknown.