With Miralem Pjanic and Sergino Dest coming in as the club's only major sigings, Koeman did claim they were trying to sign a couple more before Monday's deadline.
However, the Catalan giants failed with a Deadline-Day move for Manchester City defender Eric Garcia while Memphis Depay also revealed he was close to joining the club.
Koeman claims the financial situation at the club hindered the chances of bringing in more players.
"The squad is okay, I'm happy with the squad I have," Koeman told Barca TV.
"We have tried to improve the squad and in some positions we could, in some others we couldn't.
"That was because of the financial situation of the club, so we have to accept it and keep working."
4. Miralem Pjanic - Juventus to Barcelona (€60million)
10. Leroy Sane - Manchester City to Bayern Munich (€45million)
9. Nathan Ake - Bournemouth to Manchester City (€45.3million)
8. Mauro Icardi - Inter Milan to Paris Saint-Germain (€50million)
7. Ben Chilwell - Leicester City to Chelsea (€50million)
6. Timo Werner - RB Leipzig to Chelsea (€53million)
5. Alvaro Morata - Chelsea to Atletic Madrid (€56million)
3. Victor Osimhen - Lille to Napoli (€70million)
2. Arthur - Barcelona to Juventus (€72million)
1. Kai Havertz - Bayer Leverkusen to Chelsea (€80million)