ON DELETE CASCADE for multiple foreign keys with Sequelize

I had to set the allowNull:false for the foreignKey for getting 'CASCADE' on deletions to work. So it should be something like this in your case:

TaskListEntry.belongsTo(TaskList, {
  onDelete: 'cascade', 
  foreignKey: { allowNull: false }    //   <-------------
  hooks: true
});

---

Given the case, that your models are in general similar to this structure from http://docs.sequelizejs.com/manual/associations.html#belongs-to-many-associations:

class User extends Model {}
User.init({}, { sequelize, modelName: 'user' })

class Project extends Model {}
Project.init({}, { sequelize, modelName: 'project' })

class UserProjects extends Model {}
UserProjects.init({
  status: DataTypes.STRING
}, { sequelize, modelName: 'userProjects' })

User.belongsToMany(Project, { through: UserProjects })
Project.belongsToMany(User, { through: UserProjects })

can you try

TaskListEntry.belongsTo(TaskList);
TaskListEntry.belongsTo(Task);

instead of

TaskListEntry.belongsToMany(TaskList);
TaskListEntry.belongsToMany(Task); 

Because, from my understanding of this problem, a single TaskListEntry record can only belong to a single Task and a single TaskList.

Or Are you trying to establish a Many-to-Many relationship here? In that case, I don't think this is the ideal way of implementation.