In his position as a Senior Agent with the Bureau of Prohibition in the Department of Internal Revenue Nelson Van Alden tackles his job with the fervor of a man possessed. He is deeply religious and is married to Rose Van Alden. Van Alden is under the command of Supervisor Elliot and partnered with Agent Eric Sebso .
- Main article: Nelson Van Alden Season 1
- Main article: Nelson Van Alden Season 2
- Main article: Nelson Van Alden Season 3
- Rose Van Alden - First wife
- Abigail Van Alden - Daughter
- Sigrid - Second wife, under assumed identities as Mr. and Mrs. Mueller
- Chester Van Alden - Son
- Lucy Danziger - Lover, mother of Abigail
- Al Capone - Employer
- Dean O'Banion - Employer (former) (deceased)
- Eli Thompson - Partner in crime
- Mike D'Angelo - Colleague, murderer
- Ralph Capone - Colleague
- Frank Capone - Colleague (deceased)
Law enforcement career
- Supervisor Elliot - Commanding officer
- Agent Sebso - Subordinate (former) (deceased)
- Agent Clarkson - Subordinate (deceased)
- Agent Sawicki - Subordinate (deceased)
- Nucky Thompson - Investigatory target (deceased)
- Arnold Rothstein - Investigatory target (deceased)
- Jimmy Darmody - Investigatory target, informant (deceased)
- Mickey Doyle - Informant (deceased)
- Margaret Schroeder - Informant (former)
- Esther Randolph - Assistant US Attorney prosecuting Nucky
- Clifford Lathrop - Department of Justice investigator assigned to Randolph
- Dick Halsey - Randolph's clerk
- Scotty Gulliver - Boss (deceased)
- Phil - Colleague (deceased)
- Hank - Colleague
- Ralph - Colleague (deceased)
- Eric Sebso: Drowned in river
- Emmett Coughlin: Suffocated
- Phil: Shot in head
- Ralph: Shot in head
- Scotty Gulliver: Shot in head
- Mrs. Mauer: "And just now -"
- Nelson: "Yes?"
- Mrs. Mauer: "A blue limousine pulls up and carts them off - her and her children"
- Nelson: "A Rolls?"
- Mrs. Mauer: "How's that?"
- Nelson: "The limousine - a Rolls Royce?" ("Family Limitation")
- "THOU HAST FULLFILLED, THE JUDGEMENT OF THE WICKED!!"
- "The roast tastes good."
- "I brought lemons."
- Mickey Doyle: "I put this whole operation together. And what do I receive? A poke up my ass."
- Nelson: "Painful." ("Under God's Power She Flourishes")
|Season one appearances|
|Boardwalk Empire||The Ivory Tower||Broadway Limited||Anastasia|
|Nights in Ballygran||Family Limitation||Home||Hold Me in Paradise|
|Belle Femme||The Emerald City||Paris Green||A Return to Normalcy|
|Season two appearances|
|21||Ourselves Alone||A Dangerous Maid||What Does the Bee Do?|
|Gimcrack & Bunkum||The Age of Reason||Peg of Old||Two Boats and a Lifeguard|
|Battle of the Century||Georgia Peaches||Under God's Power She Flourishes||To the Lost|
|Season three appearances|
|"Resolution"||"Spaghetti and Coffee"||"Bone for Tuna"||"Blue Bell Boy"|
|"You'd Be Surprised"||"Ging Gang Goolie"||"Sunday Best"||"The Pony"|
|"The Milkmaid's Lot"||"A Man, A Plan..."||"Two Imposters"||"Margate Sands"|
|Season four appearances|
|"New York Sour"||"Resignation"||"Acres of Diamonds"||"All In"|
|"Erlkonig"||"The North Star"||"William Wilson"||"The Old Ship of Zion"|
|"Marriage and Hunting"||"White Horse Pike"||"Havre De Grace"||"Farewell Daddy Blues"|
|Season five appearances|
|Golden Days for Boys and Girls||The Good Listener||What Jesus Said||Cuanto|
|King of Norway||Devil You Know||Friendless Child||Eldorado|