Rio 2016 Paralympics said Monday that 1.5 million tickets had been sold and they hope that all 2.5 million will go.
The Games have been overshadowed by financial worries and the slow sale of tickets. But organisers have reported a dramatic turnaround in sales since the end of the Rio Olympics on 21 August.
At that stage only 300,000 tickets had been sold. But on Monday, organisers said in a statement the "Games achieved an important milestone as it reached 1.5 million tickets sold."
They added: "While there are still around one million tickets available the rhythm of sales suggests that all the 2.5 million tickets will be sold."
Organisers said the Olympics and hopes for Brazilian gold medals had boosted sales.
"Now we see people, look for specific athletes and scheduled duels," said Rio 2016 spokesman Mario Andrada.
Brazil are aiming for a top-five place in the medals table and have several hopes in the Paralympics athletics, including Odair Santos, who could get their first gold in the 5,000m T11 on Thursday.
The Games start on Wednesday with more than 4,300 para-athletes scheduled to take part in 22 sports.